since: 2.0 -

since: 2.1 -

 public StringUtils() 
{
                                          
        super();
}

StringUtils instances should NOT be constructed in standard programming. Instead, the class should be used as StringUtils.trim(" foo ");.

This constructor is public to permit tools that require a JavaBean instance to operate.

 public static String abbreviate(String str,
    int maxWidth) 
{
        return abbreviate(str, 0, maxWidth);
}

Abbreviates a String using ellipses. This will turn "Now is the time for all good men" into "Now is the time for..."

Specifically:

• If str is less than maxWidth characters long, return it.
• Else abbreviate it to (substring(str, 0, max-3) + "...").
• If maxWidth is less than 4, throw an IllegalArgumentException.
• In no case will it return a String of length greater than maxWidth.

StringUtils.abbreviate(null, *) = null
StringUtils.abbreviate("", 4) = ""
StringUtils.abbreviate("abcdefg", 6) = "abc..."
StringUtils.abbreviate("abcdefg", 7) = "abcdefg"
StringUtils.abbreviate("abcdefg", 8) = "abcdefg"
StringUtils.abbreviate("abcdefg", 4) = "a..."
StringUtils.abbreviate("abcdefg", 3) = IllegalArgumentException

 public static String abbreviate(String str,
    int offset,
    int maxWidth) 
{
        if (str == null) {
            return null;
        }
        if (maxWidth <  4) {
            throw new IllegalArgumentException("Minimum abbreviation width is 4");
        }
        if (str.length() < = maxWidth) {
            return str;
        }
        if (offset  > str.length()) {
            offset = str.length();
        }
        if ((str.length() - offset) <  (maxWidth - 3)) {
            offset = str.length() - (maxWidth - 3);
        }
        if (offset < = 4) {
            return str.substring(0, maxWidth - 3) + "...";
        }
        if (maxWidth <  7) {
            throw new IllegalArgumentException("Minimum abbreviation width with offset is 7");
        }
        if ((offset + (maxWidth - 3)) <  str.length()) {
            return "..." + abbreviate(str.substring(offset), maxWidth - 3);
        }
        return "..." + str.substring(str.length() - (maxWidth - 3));
}

Abbreviates a String using ellipses. This will turn "Now is the time for all good men" into "...is the time for..."

Works like abbreviate(String, int), but allows you to specify a "left edge" offset. Note that this left edge is not necessarily going to be the leftmost character in the result, or the first character following the ellipses, but it will appear somewhere in the result.

In no case will it return a String of length greater than maxWidth.

StringUtils.abbreviate(null, *, *) = null
StringUtils.abbreviate("", 0, 4) = ""
StringUtils.abbreviate("abcdefghijklmno", -1, 10) = "abcdefg..."
StringUtils.abbreviate("abcdefghijklmno", 0, 10) = "abcdefg..."
StringUtils.abbreviate("abcdefghijklmno", 1, 10) = "abcdefg..."
StringUtils.abbreviate("abcdefghijklmno", 4, 10) = "abcdefg..."
StringUtils.abbreviate("abcdefghijklmno", 5, 10) = "...fghi..."
StringUtils.abbreviate("abcdefghijklmno", 6, 10) = "...ghij..."
StringUtils.abbreviate("abcdefghijklmno", 8, 10) = "...ijklmno"
StringUtils.abbreviate("abcdefghijklmno", 10, 10) = "...ijklmno"
StringUtils.abbreviate("abcdefghijklmno", 12, 10) = "...ijklmno"
StringUtils.abbreviate("abcdefghij", 0, 3) = IllegalArgumentException
StringUtils.abbreviate("abcdefghij", 5, 6) = IllegalArgumentException

 public static String capitalise(String str) 
{
        return capitalize(str);
}

Capitalizes a String changing the first letter to title case as per Character#toTitleCase(char) . No other letters are changed.

 public static String capitaliseAllWords(String str) 
{
        return WordUtils.capitalize(str);
}

Capitalizes all the whitespace separated words in a String. Only the first letter of each word is changed.

Whitespace is defined by Character#isWhitespace(char) . A null input String returns null.

 public static String capitalize(String str) 
{
        int strLen;
        if (str == null || (strLen = str.length()) == 0) {
            return str;
        }
        return new StringBuffer(strLen)
            .append(Character.toTitleCase(str.charAt(0)))
            .append(str.substring(1))
            .toString();
}

Capitalizes a String changing the first letter to title case as per Character#toTitleCase(char) . No other letters are changed.

For a word based algorithm, see WordUtils#capitalize(String) . A null input String returns null.

StringUtils.capitalize(null) = null
StringUtils.capitalize("") = ""
StringUtils.capitalize("cat") = "Cat"
StringUtils.capitalize("cAt") = "CAt"

 public static String center(String str,
    int size) 
{
        return center(str, size, ' ");
}

Centers a String in a larger String of size size using the space character (' ').

If the size is less than the String length, the String is returned. A null String returns null. A negative size is treated as zero.

Equivalent to center(str, size, " ").

StringUtils.center(null, *) = null
StringUtils.center("", 4) = " "
StringUtils.center("ab", -1) = "ab"
StringUtils.center("ab", 4) = " ab "
StringUtils.center("abcd", 2) = "abcd"
StringUtils.center("a", 4) = " a "

 public static String center(String str,
    int size,
    char padChar) 
{
        if (str == null || size < = 0) {
            return str;
        }
        int strLen = str.length();
        int pads = size - strLen;
        if (pads < = 0) {
            return str;
        }
        str = leftPad(str, strLen + pads / 2, padChar);
        str = rightPad(str, size, padChar);
        return str;
}

Centers a String in a larger String of size size. Uses a supplied character as the value to pad the String with.

If the size is less than the String length, the String is returned. A null String returns null. A negative size is treated as zero.

StringUtils.center(null, *, *) = null
StringUtils.center("", 4, ' ') = " "
StringUtils.center("ab", -1, ' ') = "ab"
StringUtils.center("ab", 4, ' ') = " ab"
StringUtils.center("abcd", 2, ' ') = "abcd"
StringUtils.center("a", 4, ' ') = " a "
StringUtils.center("a", 4, 'y') = "yayy"

 public static String center(String str,
    int size,
    String padStr) 
{
        if (str == null || size < = 0) {
            return str;
        }
        if (isEmpty(padStr)) {
            padStr = " ";
        }
        int strLen = str.length();
        int pads = size - strLen;
        if (pads < = 0) {
            return str;
        }
        str = leftPad(str, strLen + pads / 2, padStr);
        str = rightPad(str, size, padStr);
        return str;
}

Centers a String in a larger String of size size. Uses a supplied String as the value to pad the String with.

If the size is less than the String length, the String is returned. A null String returns null. A negative size is treated as zero.

StringUtils.center(null, *, *) = null
StringUtils.center("", 4, " ") = " "
StringUtils.center("ab", -1, " ") = "ab"
StringUtils.center("ab", 4, " ") = " ab"
StringUtils.center("abcd", 2, " ") = "abcd"
StringUtils.center("a", 4, " ") = " a "
StringUtils.center("a", 4, "yz") = "yayz"
StringUtils.center("abc", 7, null) = " abc "
StringUtils.center("abc", 7, "") = " abc "

 public static String chomp(String str) 
{
        if (isEmpty(str)) {
            return str;
        }
        if (str.length() == 1) {
            char ch = str.charAt(0);
            if (ch == CharUtils.CR || ch == CharUtils.LF) {
                return EMPTY;
            }
            return str;
        }
        int lastIdx = str.length() - 1;
        char last = str.charAt(lastIdx);
        if (last == CharUtils.LF) {
            if (str.charAt(lastIdx - 1) == CharUtils.CR) {
                lastIdx--;
            }
        } else if (last != CharUtils.CR) {
            lastIdx++;
        }
        return str.substring(0, lastIdx);
}

Removes one newline from end of a String if it's there, otherwise leave it alone. A newline is "\n", "\r", or "\r\n".

NOTE: This method changed in 2.0. It now more closely matches Perl chomp.

StringUtils.chomp(null) = null
StringUtils.chomp("") = ""
StringUtils.chomp("abc \r") = "abc "
StringUtils.chomp("abc\n") = "abc"
StringUtils.chomp("abc\r\n") = "abc"
StringUtils.chomp("abc\r\n\r\n") = "abc\r\n"
StringUtils.chomp("abc\n\r") = "abc\n"
StringUtils.chomp("abc\n\rabc") = "abc\n\rabc"
StringUtils.chomp("\r") = ""
StringUtils.chomp("\n") = ""
StringUtils.chomp("\r\n") = ""

 public static String chomp(String str,
    String separator) 
{
        if (isEmpty(str) || separator == null) {
            return str;
        }
        if (str.endsWith(separator)) {
            return str.substring(0, str.length() - separator.length());
        }
        return str;
}

Removes separator from the end of str if it's there, otherwise leave it alone.

NOTE: This method changed in version 2.0. It now more closely matches Perl chomp. For the previous behavior, use #substringBeforeLast(String, String) . This method uses String#endsWith(String) .

StringUtils.chomp(null, *) = null
StringUtils.chomp("", *) = ""
StringUtils.chomp("foobar", "bar") = "foo"
StringUtils.chomp("foobar", "baz") = "foobar"
StringUtils.chomp("foo", "foo") = ""
StringUtils.chomp("foo ", "foo") = "foo "
StringUtils.chomp(" foo", "foo") = " "
StringUtils.chomp("foo", "foooo") = "foo"
StringUtils.chomp("foo", "") = "foo"
StringUtils.chomp("foo", null) = "foo"

 public static String chompLast(String str) 
{
        return chompLast(str, "\n");
}

Remove any "\n" if and only if it is at the end of the supplied String.

 public static String chompLast(String str,
    String sep) 
{
        if (str.length() == 0) {
            return str;
        }
        String sub = str.substring(str.length() - sep.length());
        if (sep.equals(sub)) {
            return str.substring(0, str.length() - sep.length());
        }
        return str;
}

Remove a value if and only if the String ends with that value.

 public static String chop(String str) 
{
        if (str == null) {
            return null;
        }
        int strLen = str.length();
        if (strLen <  2) {
            return EMPTY;
        }
        int lastIdx = strLen - 1;
        String ret = str.substring(0, lastIdx);
        char last = str.charAt(lastIdx);
        if (last == CharUtils.LF) {
            if (ret.charAt(lastIdx - 1) == CharUtils.CR) {
                return ret.substring(0, lastIdx - 1);
            }
        }
        return ret;
}

Remove the last character from a String.

If the String ends in \r\n, then remove both of them.

StringUtils.chop(null) = null
StringUtils.chop("") = ""
StringUtils.chop("abc \r") = "abc "
StringUtils.chop("abc\n") = "abc"
StringUtils.chop("abc\r\n") = "abc"
StringUtils.chop("abc") = "ab"
StringUtils.chop("abc\nabc") = "abc\nab"
StringUtils.chop("a") = ""
StringUtils.chop("\r") = ""
StringUtils.chop("\n") = ""
StringUtils.chop("\r\n") = ""

 public static String chopNewline(String str) 
{
        int lastIdx = str.length() - 1;
        if (lastIdx < = 0) {
            return EMPTY;
        }
        char last = str.charAt(lastIdx);
        if (last == CharUtils.LF) {
            if (str.charAt(lastIdx - 1) == CharUtils.CR) {
                lastIdx--;
            }
        } else {
            lastIdx++;
        }
        return str.substring(0, lastIdx);
}

Removes \n from end of a String if it's there. If a \r precedes it, then remove that too.

 public static String clean(String str) 
{
        return str == null ? EMPTY : str.trim();
}

Removes control characters (char <= 32) from both ends of this String, handling null by returning an empty String ("").

StringUtils.clean(null) = ""
StringUtils.clean("") = ""
StringUtils.clean("abc") = "abc"
StringUtils.clean(" abc ") = "abc"
StringUtils.clean(" ") = ""

 public static String concatenate(Object[] array) 
{
        return join(array, null);
}

Concatenates elements of an array into a single String. Null objects or empty strings within the array are represented by empty strings.

StringUtils.concatenate(null) = null
StringUtils.concatenate([]) = ""
StringUtils.concatenate([null]) = ""
StringUtils.concatenate(["a", "b", "c"]) = "abc"
StringUtils.concatenate([null, "", "a"]) = "a"

 public static boolean contains(String str,
    char searchChar) 
{
        if (isEmpty(str)) {
            return false;
        }
        return str.indexOf(searchChar)  >= 0;
}

Checks if String contains a search character, handling null. This method uses String#indexOf(int) .

A null or empty ("") String will return false.

StringUtils.contains(null, *) = false
StringUtils.contains("", *) = false
StringUtils.contains("abc", 'a') = true
StringUtils.contains("abc", 'z') = false

 public static boolean contains(String str,
    String searchStr) 
{
        if (str == null || searchStr == null) {
            return false;
        }
        return str.indexOf(searchStr)  >= 0;
}

Checks if String contains a search String, handling null. This method uses String#indexOf(String) .

A null String will return false.

StringUtils.contains(null, *) = false
StringUtils.contains(*, null) = false
StringUtils.contains("", "") = true
StringUtils.contains("abc", "") = true
StringUtils.contains("abc", "a") = true
StringUtils.contains("abc", "z") = false

 public static boolean containsAny(String str,
    char[] searchChars) 
{
        if (str == null || str.length() == 0 || searchChars == null || searchChars.length == 0) {
            return false;
        }
        for (int i = 0; i <  str.length(); i++) {
            char ch = str.charAt(i);
            for (int j = 0; j <  searchChars.length; j++) {
                if (searchChars[j] == ch) {
                    return true;
                }
            }
        }
        return false;
}

Checks if the String contains any character in the given set of characters.

A null String will return false. A null or zero length search array will return false.

StringUtils.containsAny(null, *) = false
StringUtils.containsAny("", *) = false
StringUtils.containsAny(*, null) = false
StringUtils.containsAny(*, []) = false
StringUtils.containsAny("zzabyycdxx",['z','a']) = true
StringUtils.containsAny("zzabyycdxx",['b','y']) = true
StringUtils.containsAny("aba", ['z']) = false

 public static boolean containsAny(String str,
    String searchChars) 
{
        if (searchChars == null) {
            return false;
        }
        return containsAny(str, searchChars.toCharArray());
}

Checks if the String contains any character in the given set of characters.

A null String will return false. A null search string will return false.

StringUtils.containsAny(null, *) = false
StringUtils.containsAny("", *) = false
StringUtils.containsAny(*, null) = false
StringUtils.containsAny(*, "") = false
StringUtils.containsAny("zzabyycdxx", "za") = true
StringUtils.containsAny("zzabyycdxx", "by") = true
StringUtils.containsAny("aba","z") = false

 public static boolean containsIgnoreCase(String str,
    String searchStr) 
{
        if (str == null || searchStr == null) {
            return false;
        }
        return contains(str.toUpperCase(), searchStr.toUpperCase());
}

Checks if String contains a search String irrespective of case, handling null. This method uses #contains(String, String) .

A null String will return false.

StringUtils.contains(null, *) = false
StringUtils.contains(*, null) = false
StringUtils.contains("", "") = true
StringUtils.contains("abc", "") = true
StringUtils.contains("abc", "a") = true
StringUtils.contains("abc", "z") = false
StringUtils.contains("abc", "A") = true
StringUtils.contains("abc", "Z") = false

 public static boolean containsNone(String str,
    char[] invalidChars) 
{
        if (str == null || invalidChars == null) {
            return true;
        }
        int strSize = str.length();
        int validSize = invalidChars.length;
        for (int i = 0; i <  strSize; i++) {
            char ch = str.charAt(i);
            for (int j = 0; j <  validSize; j++) {
                if (invalidChars[j] == ch) {
                    return false;
                }
            }
        }
        return true;
}

Checks that the String does not contain certain characters.

A null String will return true. A null invalid character array will return true. An empty String ("") always returns true.

StringUtils.containsNone(null, *) = true
StringUtils.containsNone(*, null) = true
StringUtils.containsNone("", *) = true
StringUtils.containsNone("ab", '') = true
StringUtils.containsNone("abab", 'xyz') = true
StringUtils.containsNone("ab1", 'xyz') = true
StringUtils.containsNone("abz", 'xyz') = false

 public static boolean containsNone(String str,
    String invalidChars) 
{
        if (str == null || invalidChars == null) {
            return true;
        }
        return containsNone(str, invalidChars.toCharArray());
}

Checks that the String does not contain certain characters.

A null String will return true. A null invalid character array will return true. An empty String ("") always returns true.

StringUtils.containsNone(null, *) = true
StringUtils.containsNone(*, null) = true
StringUtils.containsNone("", *) = true
StringUtils.containsNone("ab", "") = true
StringUtils.containsNone("abab", "xyz") = true
StringUtils.containsNone("ab1", "xyz") = true
StringUtils.containsNone("abz", "xyz") = false

 public static boolean containsOnly(String str,
    char[] valid) 
{
        // All these pre-checks are to maintain API with an older version
        if ((valid == null) || (str == null)) {
            return false;
        }
        if (str.length() == 0) {
            return true;
        }
        if (valid.length == 0) {
            return false;
        }
        return indexOfAnyBut(str, valid) == -1;
}

Checks if the String contains only certain characters.

A null String will return false. A null valid character array will return false. An empty String ("") always returns true.

StringUtils.containsOnly(null, *) = false
StringUtils.containsOnly(*, null) = false
StringUtils.containsOnly("", *) = true
StringUtils.containsOnly("ab", '') = false
StringUtils.containsOnly("abab", 'abc') = true
StringUtils.containsOnly("ab1", 'abc') = false
StringUtils.containsOnly("abz", 'abc') = false

 public static boolean containsOnly(String str,
    String validChars) 
{
        if (str == null || validChars == null) {
            return false;
        }
        return containsOnly(str, validChars.toCharArray());
}

Checks if the String contains only certain characters.

A null String will return false. A null valid character String will return false. An empty String ("") always returns true.

StringUtils.containsOnly(null, *) = false
StringUtils.containsOnly(*, null) = false
StringUtils.containsOnly("", *) = true
StringUtils.containsOnly("ab", "") = false
StringUtils.containsOnly("abab", "abc") = true
StringUtils.containsOnly("ab1", "abc") = false
StringUtils.containsOnly("abz", "abc") = false

 public static int countMatches(String str,
    String sub) 
{
        if (isEmpty(str) || isEmpty(sub)) {
            return 0;
        }
        int count = 0;
        int idx = 0;
        while ((idx = str.indexOf(sub, idx)) != -1) {
            count++;
            idx += sub.length();
        }
        return count;
}

Counts how many times the substring appears in the larger String.

A null or empty ("") String input returns 0.

StringUtils.countMatches(null, *) = 0
StringUtils.countMatches("", *) = 0
StringUtils.countMatches("abba", null) = 0
StringUtils.countMatches("abba", "") = 0
StringUtils.countMatches("abba", "a") = 2
StringUtils.countMatches("abba", "ab") = 1
StringUtils.countMatches("abba", "xxx") = 0

 public static String defaultIfEmpty(String str,
    String defaultStr) 
{
        return StringUtils.isEmpty(str) ? defaultStr : str;
}

Returns either the passed in String, or if the String is empty or null, the value of defaultStr.

StringUtils.defaultIfEmpty(null, "NULL") = "NULL"
StringUtils.defaultIfEmpty("", "NULL") = "NULL"
StringUtils.defaultIfEmpty("bat", "NULL") = "bat"

 public static String defaultString(String str) 
{
        return str == null ? EMPTY : str;
}

Returns either the passed in String, or if the String is null, an empty String ("").

StringUtils.defaultString(null) = ""
StringUtils.defaultString("") = ""
StringUtils.defaultString("bat") = "bat"

 public static String defaultString(String str,
    String defaultStr) 
{
        return str == null ? defaultStr : str;
}

Returns either the passed in String, or if the String is null, the value of defaultStr.

StringUtils.defaultString(null, "NULL") = "NULL"
StringUtils.defaultString("", "NULL") = ""
StringUtils.defaultString("bat", "NULL") = "bat"

 public static String deleteSpaces(String str) 
{
        if (str == null) {
            return null;
        }
        return CharSetUtils.delete(str, " \t\r\n\b");
}

Deletes all 'space' characters from a String as defined by Character#isSpace(char) .

This is the only StringUtils method that uses the isSpace definition. You are advised to use #deleteWhitespace(String) instead as whitespace is much better localized.

StringUtils.deleteSpaces(null) = null
StringUtils.deleteSpaces("") = ""
StringUtils.deleteSpaces("abc") = "abc"
StringUtils.deleteSpaces(" \t abc \n ") = "abc"
StringUtils.deleteSpaces("ab c") = "abc"
StringUtils.deleteSpaces("a\nb\tc ") = "abc"

Spaces are defined as {' ', '\t', '\r', '\n', '\b'} in line with the deprecated isSpace method.

 public static String deleteWhitespace(String str) 
{
        if (isEmpty(str)) {
            return str;
        }
        int sz = str.length();
        char[] chs = new char[sz];
        int count = 0;
        for (int i = 0; i <  sz; i++) {
            if (!Character.isWhitespace(str.charAt(i))) {
                chs[count++] = str.charAt(i);
            }
        }
        if (count == sz) {
            return str;
        }
        return new String(chs, 0, count);
}

Deletes all whitespaces from a String as defined by Character#isWhitespace(char) .

StringUtils.deleteWhitespace(null) = null
StringUtils.deleteWhitespace("") = ""
StringUtils.deleteWhitespace("abc") = "abc"
StringUtils.deleteWhitespace(" ab c ") = "abc"

 public static String difference(String str1,
    String str2) 
{
        if (str1 == null) {
            return str2;
        }
        if (str2 == null) {
            return str1;
        }
        int at = indexOfDifference(str1, str2);
        if (at == -1) {
            return EMPTY;
        }
        return str2.substring(at);
}

Compares two Strings, and returns the portion where they differ. (More precisely, return the remainder of the second String, starting from where it's different from the first.)

For example, difference("i am a machine", "i am a robot") -> "robot".

StringUtils.difference(null, null) = null
StringUtils.difference("", "") = ""
StringUtils.difference("", "abc") = "abc"
StringUtils.difference("abc", "") = ""
StringUtils.difference("abc", "abc") = ""
StringUtils.difference("ab", "abxyz") = "xyz"
StringUtils.difference("abcde", "abxyz") = "xyz"
StringUtils.difference("abcde", "xyz") = "xyz"

 public static boolean endsWith(String str,
    String suffix) 
{
        return endsWith(str, suffix, false);
}

Check if a String ends with a specified suffix.

nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case sensitive.

StringUtils.endsWith(null, null) = true
StringUtils.endsWith(null, "abcdef") = false
StringUtils.endsWith("def", null) = false
StringUtils.endsWith("def", "abcdef") = true
StringUtils.endsWith("def", "ABCDEF") = false

 public static boolean endsWithIgnoreCase(String str,
    String suffix) 
{
        return endsWith(str, suffix, true);
}

Case insensitive check if a String ends with a specified suffix.

nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case insensitive.

StringUtils.endsWithIgnoreCase(null, null) = true
StringUtils.endsWithIgnoreCase(null, "abcdef") = false
StringUtils.endsWithIgnoreCase("def", null) = false
StringUtils.endsWithIgnoreCase("def", "abcdef") = true
StringUtils.endsWithIgnoreCase("def", "ABCDEF") = false

 public static boolean equals(String str1,
    String str2) 
{
        return str1 == null ? str2 == null : str1.equals(str2);
}

Compares two Strings, returning true if they are equal.

nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case sensitive.

StringUtils.equals(null, null) = true
StringUtils.equals(null, "abc") = false
StringUtils.equals("abc", null) = false
StringUtils.equals("abc", "abc") = true
StringUtils.equals("abc", "ABC") = false

 public static boolean equalsIgnoreCase(String str1,
    String str2) 
{
        return str1 == null ? str2 == null : str1.equalsIgnoreCase(str2);
}

Compares two Strings, returning true if they are equal ignoring the case.

nulls are handled without exceptions. Two null references are considered equal. Comparison is case insensitive.

StringUtils.equalsIgnoreCase(null, null) = true
StringUtils.equalsIgnoreCase(null, "abc") = false
StringUtils.equalsIgnoreCase("abc", null) = false
StringUtils.equalsIgnoreCase("abc", "abc") = true
StringUtils.equalsIgnoreCase("abc", "ABC") = true

 public static String escape(String str) 
{
        return StringEscapeUtils.escapeJava(str);
}

Escapes any values it finds into their String form.

So a tab becomes the characters '\\' and 't'.

As of Lang 2.0, this calls StringEscapeUtils#escapeJava(String) behind the scenes.

 public static String getChomp(String str,
    String sep) 
{
        int idx = str.lastIndexOf(sep);
        if (idx == str.length() - sep.length()) {
            return sep;
        } else if (idx != -1) {
            return str.substring(idx);
        } else {
            return EMPTY;
        }
}

Remove everything and return the last value of a supplied String, and everything after it from a String.

 public static String getCommonPrefix(String[] strs) 
{
        if (strs == null || strs.length == 0) {
            return EMPTY;
        }
        int smallestIndexOfDiff = indexOfDifference(strs);
        if (smallestIndexOfDiff == -1) {
            // all strings were identical
            if (strs[0] == null) {
                return EMPTY;
            }
            return strs[0];
        } else if (smallestIndexOfDiff == 0) {
            // there were no common initial characters
            return EMPTY;
        } else {
            // we found a common initial character sequence
            return strs[0].substring(0, smallestIndexOfDiff);
        }
}

Compares all Strings in an array and returns the initial sequence of characters that is common to all of them.

For example, getCommonPrefix(new String[] {"i am a machine", "i am a robot"}) -> "i am a "

StringUtils.getCommonPrefix(null) = ""
StringUtils.getCommonPrefix(new String[] {}) = ""
StringUtils.getCommonPrefix(new String[] {"abc"}) = "abc"
StringUtils.getCommonPrefix(new String[] {null, null}) = ""
StringUtils.getCommonPrefix(new String[] {"", ""}) = ""
StringUtils.getCommonPrefix(new String[] {"", null}) = ""
StringUtils.getCommonPrefix(new String[] {"abc", null, null}) = ""
StringUtils.getCommonPrefix(new String[] {null, null, "abc"}) = ""
StringUtils.getCommonPrefix(new String[] {"", "abc"}) = ""
StringUtils.getCommonPrefix(new String[] {"abc", ""}) = ""
StringUtils.getCommonPrefix(new String[] {"abc", "abc"}) = "abc"
StringUtils.getCommonPrefix(new String[] {"abc", "a"}) = "a"
StringUtils.getCommonPrefix(new String[] {"ab", "abxyz"}) = "ab"
StringUtils.getCommonPrefix(new String[] {"abcde", "abxyz"}) = "ab"
StringUtils.getCommonPrefix(new String[] {"abcde", "xyz"}) = ""
StringUtils.getCommonPrefix(new String[] {"xyz", "abcde"}) = ""
StringUtils.getCommonPrefix(new String[] {"i am a machine", "i am a robot"}) = "i am a "

 public static int getLevenshteinDistance(String s,
    String t) 
{
        if (s == null || t == null) {
            throw new IllegalArgumentException("Strings must not be null");
        }
        /*
           The difference between this impl. and the previous is that, rather 
           than creating and retaining a matrix of size s.length()+1 by t.length()+1, 
           we maintain two single-dimensional arrays of length s.length()+1.  The first, d,
           is the 'current working' distance array that maintains the newest distance cost
           counts as we iterate through the characters of String s.  Each time we increment
           the index of String t we are comparing, d is copied to p, the second int[].  Doing so
           allows us to retain the previous cost counts as required by the algorithm (taking 
           the minimum of the cost count to the left, up one, and diagonally up and to the left
           of the current cost count being calculated).  (Note that the arrays aren't really 
           copied anymore, just switched...this is clearly much better than cloning an array 
           or doing a System.arraycopy() each time  through the outer loop.)
           Effectively, the difference between the two implementations is this one does not 
           cause an out of memory condition when calculating the LD over two very large strings.
         */
        int n = s.length(); // length of s
        int m = t.length(); // length of t
        if (n == 0) {
            return m;
        } else if (m == 0) {
            return n;
        }
        if (n  > m) {
            // swap the input strings to consume less memory
            String tmp = s;
            s = t;
            t = tmp;
            n = m;
            m = t.length();
        }
        int p[] = new int[n+1]; //'previous' cost array, horizontally
        int d[] = new int[n+1]; // cost array, horizontally
        int _d[]; //placeholder to assist in swapping p and d
        // indexes into strings s and t
        int i; // iterates through s
        int j; // iterates through t
        char t_j; // jth character of t
        int cost; // cost
        for (i = 0; i< =n; i++) {
            p[i] = i;
        }
        for (j = 1; j< =m; j++) {
            t_j = t.charAt(j-1);
            d[0] = j;
            for (i=1; i< =n; i++) {
                cost = s.charAt(i-1)==t_j ? 0 : 1;
                // minimum of cell to the left+1, to the top+1, diagonally left and up +cost
                d[i] = Math.min(Math.min(d[i-1]+1, p[i]+1),  p[i-1]+cost);
            }
            // copy current distance counts to 'previous row' distance counts
            _d = p;
            p = d;
            d = _d;
        }
        // our last action in the above loop was to switch d and p, so p now 
        // actually has the most recent cost counts
        return p[n];
}

Find the Levenshtein distance between two Strings.

This is the number of changes needed to change one String into another, where each change is a single character modification (deletion, insertion or substitution).

The previous implementation of the Levenshtein distance algorithm was from http://www.merriampark.com/ld.htm

Chas Emerick has written an implementation in Java, which avoids an OutOfMemoryError which can occur when my Java implementation is used with very large strings.
This implementation of the Levenshtein distance algorithm is from http://www.merriampark.com/ldjava.htm

StringUtils.getLevenshteinDistance(null, *) = IllegalArgumentException
StringUtils.getLevenshteinDistance(*, null) = IllegalArgumentException
StringUtils.getLevenshteinDistance("","") = 0
StringUtils.getLevenshteinDistance("","a") = 1
StringUtils.getLevenshteinDistance("aaapppp", "") = 7
StringUtils.getLevenshteinDistance("frog", "fog") = 1
StringUtils.getLevenshteinDistance("fly", "ant") = 3
StringUtils.getLevenshteinDistance("elephant", "hippo") = 7
StringUtils.getLevenshteinDistance("hippo", "elephant") = 7
StringUtils.getLevenshteinDistance("hippo", "zzzzzzzz") = 8
StringUtils.getLevenshteinDistance("hello", "hallo") = 1

 public static String getNestedString(String str,
    String tag) 
{
        return substringBetween(str, tag, tag);
}

Gets the String that is nested in between two instances of the same String.

A null input String returns null. A null tag returns null.

StringUtils.getNestedString(null, *) = null
StringUtils.getNestedString("", "") = ""
StringUtils.getNestedString("", "tag") = null
StringUtils.getNestedString("tagabctag", null) = null
StringUtils.getNestedString("tagabctag", "") = ""
StringUtils.getNestedString("tagabctag", "tag") = "abc"

 public static String getNestedString(String str,
    String open,
    String close) 
{
        return substringBetween(str, open, close);
}

Gets the String that is nested in between two Strings. Only the first match is returned.

A null input String returns null. A null open/close returns null (no match). An empty ("") open/close returns an empty string.

StringUtils.getNestedString(null, *, *) = null
StringUtils.getNestedString("", "", "") = ""
StringUtils.getNestedString("", "", "tag") = null
StringUtils.getNestedString("", "tag", "tag") = null
StringUtils.getNestedString("yabcz", null, null) = null
StringUtils.getNestedString("yabcz", "", "") = ""
StringUtils.getNestedString("yabcz", "y", "z") = "abc"
StringUtils.getNestedString("yabczyabcz", "y", "z") = "abc"

 public static String getPrechomp(String str,
    String sep) 
{
        int idx = str.indexOf(sep);
        if (idx == -1) {
            return EMPTY;
        } 
        return str.substring(0, idx + sep.length());
}

Remove and return everything before the first value of a supplied String from another String.

 public static int indexOf(String str,
    char searchChar) 
{
        if (isEmpty(str)) {
            return -1;
        }
        return str.indexOf(searchChar);
}

Finds the first index within a String, handling null. This method uses String#indexOf(int) .

A null or empty ("") String will return -1.

StringUtils.indexOf(null, *) = -1
StringUtils.indexOf("", *) = -1
StringUtils.indexOf("aabaabaa", 'a') = 0
StringUtils.indexOf("aabaabaa", 'b') = 2

 public static int indexOf(String str,
    String searchStr) 
{
        if (str == null || searchStr == null) {
            return -1;
        }
        return str.indexOf(searchStr);
}

Finds the first index within a String, handling null. This method uses String#indexOf(String) .

A null String will return -1.

StringUtils.indexOf(null, *) = -1
StringUtils.indexOf(*, null) = -1
StringUtils.indexOf("", "") = 0
StringUtils.indexOf("aabaabaa", "a") = 0
StringUtils.indexOf("aabaabaa", "b") = 2
StringUtils.indexOf("aabaabaa", "ab") = 1
StringUtils.indexOf("aabaabaa", "") = 0

 public static int indexOf(String str,
    char searchChar,
    int startPos) 
{
        if (isEmpty(str)) {
            return -1;
        }
        return str.indexOf(searchChar, startPos);
}

Finds the first index within a String from a start position, handling null. This method uses String#indexOf(int, int) .

A null or empty ("") String will return -1. A negative start position is treated as zero. A start position greater than the string length returns -1.

StringUtils.indexOf(null, *, *) = -1
StringUtils.indexOf("", *, *) = -1
StringUtils.indexOf("aabaabaa", 'b', 0) = 2
StringUtils.indexOf("aabaabaa", 'b', 3) = 5
StringUtils.indexOf("aabaabaa", 'b', 9) = -1
StringUtils.indexOf("aabaabaa", 'b', -1) = 2

 public static int indexOf(String str,
    String searchStr,
    int startPos) 
{
        if (str == null || searchStr == null) {
            return -1;
        }
        // JDK1.2/JDK1.3 have a bug, when startPos  > str.length for "", hence
        if (searchStr.length() == 0 && startPos  >= str.length()) {
            return str.length();
        }
        return str.indexOf(searchStr, startPos);
}

Finds the first index within a String, handling null. This method uses String#indexOf(String, int) .

A null String will return -1. A negative start position is treated as zero. An empty ("") search String always matches. A start position greater than the string length only matches an empty search String.

StringUtils.indexOf(null, *, *) = -1
StringUtils.indexOf(*, null, *) = -1
StringUtils.indexOf("", "", 0) = 0
StringUtils.indexOf("aabaabaa", "a", 0) = 0
StringUtils.indexOf("aabaabaa", "b", 0) = 2
StringUtils.indexOf("aabaabaa", "ab", 0) = 1
StringUtils.indexOf("aabaabaa", "b", 3) = 5
StringUtils.indexOf("aabaabaa", "b", 9) = -1
StringUtils.indexOf("aabaabaa", "b", -1) = 2
StringUtils.indexOf("aabaabaa", "", 2) = 2
StringUtils.indexOf("abc", "", 9) = 3

 public static int indexOfAny(String str,
    char[] searchChars) 
{
        if (isEmpty(str) || ArrayUtils.isEmpty(searchChars)) {
            return -1;
        }
        for (int i = 0; i <  str.length(); i++) {
            char ch = str.charAt(i);
            for (int j = 0; j <  searchChars.length; j++) {
                if (searchChars[j] == ch) {
                    return i;
                }
            }
        }
        return -1;
}

Search a String to find the first index of any character in the given set of characters.

A null String will return -1. A null or zero length search array will return -1.

StringUtils.indexOfAny(null, *) = -1
StringUtils.indexOfAny("", *) = -1
StringUtils.indexOfAny(*, null) = -1
StringUtils.indexOfAny(*, []) = -1
StringUtils.indexOfAny("zzabyycdxx",['z','a']) = 0
StringUtils.indexOfAny("zzabyycdxx",['b','y']) = 3
StringUtils.indexOfAny("aba", ['z']) = -1

 public static int indexOfAny(String str,
    String searchChars) 
{
        if (isEmpty(str) || isEmpty(searchChars)) {
            return -1;
        }
        return indexOfAny(str, searchChars.toCharArray());
}

Search a String to find the first index of any character in the given set of characters.

A null String will return -1. A null search string will return -1.

StringUtils.indexOfAny(null, *) = -1
StringUtils.indexOfAny("", *) = -1
StringUtils.indexOfAny(*, null) = -1
StringUtils.indexOfAny(*, "") = -1
StringUtils.indexOfAny("zzabyycdxx", "za") = 0
StringUtils.indexOfAny("zzabyycdxx", "by") = 3
StringUtils.indexOfAny("aba","z") = -1

 public static int indexOfAny(String str,
    String[] searchStrs) 
{
        if ((str == null) || (searchStrs == null)) {
            return -1;
        }
        int sz = searchStrs.length;
        // String's can't have a MAX_VALUEth index.
        int ret = Integer.MAX_VALUE;
        int tmp = 0;
        for (int i = 0; i <  sz; i++) {
            String search = searchStrs[i];
            if (search == null) {
                continue;
            }
            tmp = str.indexOf(search);
            if (tmp == -1) {
                continue;
            }
            if (tmp <  ret) {
                ret = tmp;
            }
        }
        return (ret == Integer.MAX_VALUE) ? -1 : ret;
}

Find the first index of any of a set of potential substrings.

A null String will return -1. A null or zero length search array will return -1. A null search array entry will be ignored, but a search array containing "" will return 0 if str is not null. This method uses String#indexOf(String) .

StringUtils.indexOfAny(null, *) = -1
StringUtils.indexOfAny(*, null) = -1
StringUtils.indexOfAny(*, []) = -1
StringUtils.indexOfAny("zzabyycdxx", ["ab","cd"]) = 2
StringUtils.indexOfAny("zzabyycdxx", ["cd","ab"]) = 2
StringUtils.indexOfAny("zzabyycdxx", ["mn","op"]) = -1
StringUtils.indexOfAny("zzabyycdxx", ["zab","aby"]) = 1
StringUtils.indexOfAny("zzabyycdxx", [""]) = 0
StringUtils.indexOfAny("", [""]) = 0
StringUtils.indexOfAny("", ["a"]) = -1

 public static int indexOfAnyBut(String str,
    char[] searchChars) 
{
        if (isEmpty(str) || ArrayUtils.isEmpty(searchChars)) {
            return -1;
        }
        outer : for (int i = 0; i <  str.length(); i++) {
            char ch = str.charAt(i);
            for (int j = 0; j <  searchChars.length; j++) {
                if (searchChars[j] == ch) {
                    continue outer;
                }
            }
            return i;
        }
        return -1;
}

Search a String to find the first index of any character not in the given set of characters.

A null String will return -1. A null or zero length search array will return -1.

StringUtils.indexOfAnyBut(null, *) = -1
StringUtils.indexOfAnyBut("", *) = -1
StringUtils.indexOfAnyBut(*, null) = -1
StringUtils.indexOfAnyBut(*, []) = -1
StringUtils.indexOfAnyBut("zzabyycdxx",'za') = 3
StringUtils.indexOfAnyBut("zzabyycdxx", '') = 0
StringUtils.indexOfAnyBut("aba", 'ab') = -1

 public static int indexOfAnyBut(String str,
    String searchChars) 
{
        if (isEmpty(str) || isEmpty(searchChars)) {
            return -1;
        }
        for (int i = 0; i <  str.length(); i++) {
            if (searchChars.indexOf(str.charAt(i)) <  0) {
                return i;
            }
        }
        return -1;
}

Search a String to find the first index of any character not in the given set of characters.

A null String will return -1. A null search string will return -1.

StringUtils.indexOfAnyBut(null, *) = -1
StringUtils.indexOfAnyBut("", *) = -1
StringUtils.indexOfAnyBut(*, null) = -1
StringUtils.indexOfAnyBut(*, "") = -1
StringUtils.indexOfAnyBut("zzabyycdxx", "za") = 3
StringUtils.indexOfAnyBut("zzabyycdxx", "") = 0
StringUtils.indexOfAnyBut("aba","ab") = -1

 public static int indexOfDifference(String[] strs) 
{
        if (strs == null || strs.length < = 1) {
            return -1;
        }
        boolean anyStringNull = false;
        boolean allStringsNull = true;
        int arrayLen = strs.length;
        int shortestStrLen = Integer.MAX_VALUE;
        int longestStrLen = 0;
        // find the min and max string lengths; this avoids checking to make
        // sure we are not exceeding the length of the string each time through
        // the bottom loop.
        for (int i = 0; i <  arrayLen; i++) {
            if (strs[i] == null) {
                anyStringNull = true;
                shortestStrLen = 0;
            } else {
                allStringsNull = false;
                shortestStrLen = Math.min(strs[i].length(), shortestStrLen);
                longestStrLen = Math.max(strs[i].length(), longestStrLen);
            }
        }
        // handle lists containing all nulls or all empty strings
        if (allStringsNull || (longestStrLen == 0 && !anyStringNull)) {
            return -1;
        }
        // handle lists containing some nulls or some empty strings
        if (shortestStrLen == 0) {
            return 0;
        }
        // find the position with the first difference across all strings
        int firstDiff = -1;
        for (int stringPos = 0; stringPos <  shortestStrLen; stringPos++) {
            char comparisonChar = strs[0].charAt(stringPos);
            for (int arrayPos = 1; arrayPos <  arrayLen; arrayPos++) {
                if (strs[arrayPos].charAt(stringPos) != comparisonChar) {
                    firstDiff = stringPos;
                    break;
                }
            }
            if (firstDiff != -1) {
                break;
            }
        }
        if (firstDiff == -1 && shortestStrLen != longestStrLen) {
            // we compared all of the characters up to the length of the
            // shortest string and didn't find a match, but the string lengths
            // vary, so return the length of the shortest string.
            return shortestStrLen;
        }
        return firstDiff;
}

Compares all Strings in an array and returns the index at which the Strings begin to differ.

For example, indexOfDifference(new String[] {"i am a machine", "i am a robot"}) -> 7

StringUtils.indexOfDifference(null) = -1
StringUtils.indexOfDifference(new String[] {}) = -1
StringUtils.indexOfDifference(new String[] {"abc"}) = -1
StringUtils.indexOfDifference(new String[] {null, null}) = -1
StringUtils.indexOfDifference(new String[] {"", ""}) = -1
StringUtils.indexOfDifference(new String[] {"", null}) = 0
StringUtils.indexOfDifference(new String[] {"abc", null, null}) = 0
StringUtils.indexOfDifference(new String[] {null, null, "abc"}) = 0
StringUtils.indexOfDifference(new String[] {"", "abc"}) = 0
StringUtils.indexOfDifference(new String[] {"abc", ""}) = 0
StringUtils.indexOfDifference(new String[] {"abc", "abc"}) = -1
StringUtils.indexOfDifference(new String[] {"abc", "a"}) = 1
StringUtils.indexOfDifference(new String[] {"ab", "abxyz"}) = 2
StringUtils.indexOfDifference(new String[] {"abcde", "abxyz"}) = 2
StringUtils.indexOfDifference(new String[] {"abcde", "xyz"}) = 0
StringUtils.indexOfDifference(new String[] {"xyz", "abcde"}) = 0
StringUtils.indexOfDifference(new String[] {"i am a machine", "i am a robot"}) = 7

 public static int indexOfDifference(String str1,
    String str2) 
{
        if (str1 == str2) {
            return -1;
        }
        if (str1 == null || str2 == null) {
            return 0;
        }
        int i;
        for (i = 0; i <  str1.length() && i <  str2.length(); ++i) {
            if (str1.charAt(i) != str2.charAt(i)) {
                break;
            }
        }
        if (i <  str2.length() || i <  str1.length()) {
            return i;
        }
        return -1;
}

Compares two Strings, and returns the index at which the Strings begin to differ.

For example, indexOfDifference("i am a machine", "i am a robot") -> 7

StringUtils.indexOfDifference(null, null) = -1
StringUtils.indexOfDifference("", "") = -1
StringUtils.indexOfDifference("", "abc") = 0
StringUtils.indexOfDifference("abc", "") = 0
StringUtils.indexOfDifference("abc", "abc") = -1
StringUtils.indexOfDifference("ab", "abxyz") = 2
StringUtils.indexOfDifference("abcde", "abxyz") = 2
StringUtils.indexOfDifference("abcde", "xyz") = 0

 public static boolean isAlpha(String str) 
{
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i <  sz; i++) {
            if (Character.isLetter(str.charAt(i)) == false) {
                return false;
            }
        }
        return true;
}

Checks if the String contains only unicode letters.

null will return false. An empty String ("") will return true.

StringUtils.isAlpha(null) = false
StringUtils.isAlpha("") = true
StringUtils.isAlpha(" ") = false
StringUtils.isAlpha("abc") = true
StringUtils.isAlpha("ab2c") = false
StringUtils.isAlpha("ab-c") = false

 public static boolean isAlphaSpace(String str) 
{
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i <  sz; i++) {
            if ((Character.isLetter(str.charAt(i)) == false) && (str.charAt(i) != ' ")) {
                return false;
            }
        }
        return true;
}

Checks if the String contains only unicode letters and space (' ').

null will return false An empty String ("") will return true.

StringUtils.isAlphaSpace(null) = false
StringUtils.isAlphaSpace("") = true
StringUtils.isAlphaSpace(" ") = true
StringUtils.isAlphaSpace("abc") = true
StringUtils.isAlphaSpace("ab c") = true
StringUtils.isAlphaSpace("ab2c") = false
StringUtils.isAlphaSpace("ab-c") = false

 public static boolean isAlphanumeric(String str) 
{
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i <  sz; i++) {
            if (Character.isLetterOrDigit(str.charAt(i)) == false) {
                return false;
            }
        }
        return true;
}

Checks if the String contains only unicode letters or digits.

null will return false. An empty String ("") will return true.

StringUtils.isAlphanumeric(null) = false
StringUtils.isAlphanumeric("") = true
StringUtils.isAlphanumeric(" ") = false
StringUtils.isAlphanumeric("abc") = true
StringUtils.isAlphanumeric("ab c") = false
StringUtils.isAlphanumeric("ab2c") = true
StringUtils.isAlphanumeric("ab-c") = false

 public static boolean isAlphanumericSpace(String str) 
{
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i <  sz; i++) {
            if ((Character.isLetterOrDigit(str.charAt(i)) == false) && (str.charAt(i) != ' ")) {
                return false;
            }
        }
        return true;
}

Checks if the String contains only unicode letters, digits or space (' ').

null will return false. An empty String ("") will return true.

StringUtils.isAlphanumeric(null) = false
StringUtils.isAlphanumeric("") = true
StringUtils.isAlphanumeric(" ") = true
StringUtils.isAlphanumeric("abc") = true
StringUtils.isAlphanumeric("ab c") = true
StringUtils.isAlphanumeric("ab2c") = true
StringUtils.isAlphanumeric("ab-c") = false

 public static boolean isAsciiPrintable(String str) 
{
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i <  sz; i++) {
            if (CharUtils.isAsciiPrintable(str.charAt(i)) == false) {
                return false;
            }
        }
        return true;
}

Checks if the string contains only ASCII printable characters.

null will return false. An empty String ("") will return true.

StringUtils.isAsciiPrintable(null) = false
StringUtils.isAsciiPrintable("") = true
StringUtils.isAsciiPrintable(" ") = true
StringUtils.isAsciiPrintable("Ceki") = true
StringUtils.isAsciiPrintable("ab2c") = true
StringUtils.isAsciiPrintable("!ab-c~") = true
StringUtils.isAsciiPrintable("\u0020") = true
StringUtils.isAsciiPrintable("\u0021") = true
StringUtils.isAsciiPrintable("\u007e") = true
StringUtils.isAsciiPrintable("\u007f") = false
StringUtils.isAsciiPrintable("Ceki G\u00fclc\u00fc") = false

 public static boolean isBlank(String str) 
{
        int strLen;
        if (str == null || (strLen = str.length()) == 0) {
            return true;
        }
        for (int i = 0; i <  strLen; i++) {
            if ((Character.isWhitespace(str.charAt(i)) == false)) {
                return false;
            }
        }
        return true;
}

Checks if a String is whitespace, empty ("") or null.

StringUtils.isBlank(null) = true
StringUtils.isBlank("") = true
StringUtils.isBlank(" ") = true
StringUtils.isBlank("bob") = false
StringUtils.isBlank(" bob ") = false

 public static boolean isEmpty(String str) 
{
        return str == null || str.length() == 0;
}

Checks if a String is empty ("") or null.

StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false

NOTE: This method changed in Lang version 2.0. It no longer trims the String. That functionality is available in isBlank().

 public static boolean isNotBlank(String str) 
{
        return !StringUtils.isBlank(str);
}

Checks if a String is not empty (""), not null and not whitespace only.

StringUtils.isNotBlank(null) = false
StringUtils.isNotBlank("") = false
StringUtils.isNotBlank(" ") = false
StringUtils.isNotBlank("bob") = true
StringUtils.isNotBlank(" bob ") = true

 public static boolean isNotEmpty(String str) 
{
        return !StringUtils.isEmpty(str);
}

Checks if a String is not empty ("") and not null.

StringUtils.isNotEmpty(null) = false
StringUtils.isNotEmpty("") = false
StringUtils.isNotEmpty(" ") = true
StringUtils.isNotEmpty("bob") = true
StringUtils.isNotEmpty(" bob ") = true

 public static boolean isNumeric(String str) 
{
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i <  sz; i++) {
            if (Character.isDigit(str.charAt(i)) == false) {
                return false;
            }
        }
        return true;
}

Checks if the String contains only unicode digits. A decimal point is not a unicode digit and returns false.

null will return false. An empty String ("") will return true.

StringUtils.isNumeric(null) = false
StringUtils.isNumeric("") = true
StringUtils.isNumeric(" ") = false
StringUtils.isNumeric("123") = true
StringUtils.isNumeric("12 3") = false
StringUtils.isNumeric("ab2c") = false
StringUtils.isNumeric("12-3") = false
StringUtils.isNumeric("12.3") = false

 public static boolean isNumericSpace(String str) 
{
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i <  sz; i++) {
            if ((Character.isDigit(str.charAt(i)) == false) && (str.charAt(i) != ' ")) {
                return false;
            }
        }
        return true;
}

Checks if the String contains only unicode digits or space (' '). A decimal point is not a unicode digit and returns false.

null will return false. An empty String ("") will return true.

StringUtils.isNumeric(null) = false
StringUtils.isNumeric("") = true
StringUtils.isNumeric(" ") = true
StringUtils.isNumeric("123") = true
StringUtils.isNumeric("12 3") = true
StringUtils.isNumeric("ab2c") = false
StringUtils.isNumeric("12-3") = false
StringUtils.isNumeric("12.3") = false

 public static boolean isWhitespace(String str) 
{
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i <  sz; i++) {
            if ((Character.isWhitespace(str.charAt(i)) == false)) {
                return false;
            }
        }
        return true;
}

Checks if the String contains only whitespace.

null will return false. An empty String ("") will return true.

StringUtils.isWhitespace(null) = false
StringUtils.isWhitespace("") = true
StringUtils.isWhitespace(" ") = true
StringUtils.isWhitespace("abc") = false
StringUtils.isWhitespace("ab2c") = false
StringUtils.isWhitespace("ab-c") = false

 public static String join(Object[] array) 
{
        return join(array, null);
}

Joins the elements of the provided array into a single String containing the provided list of elements.

No separator is added to the joined String. Null objects or empty strings within the array are represented by empty strings.

StringUtils.join(null) = null
StringUtils.join([]) = ""
StringUtils.join([null]) = ""
StringUtils.join(["a", "b", "c"]) = "abc"
StringUtils.join([null, "", "a"]) = "a"

 public static String join(Object[] array,
    char separator) 
{
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
}

Joins the elements of the provided array into a single String containing the provided list of elements.

No delimiter is added before or after the list. Null objects or empty strings within the array are represented by empty strings.

StringUtils.join(null, *) = null
StringUtils.join([], *) = ""
StringUtils.join([null], *) = ""
StringUtils.join(["a", "b", "c"], ';') = "a;b;c"
StringUtils.join(["a", "b", "c"], null) = "abc"
StringUtils.join([null, "", "a"], ';') = ";;a"

 public static String join(Object[] array,
    String separator) 
{
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
}

Joins the elements of the provided array into a single String containing the provided list of elements.

No delimiter is added before or after the list. A null separator is the same as an empty String (""). Null objects or empty strings within the array are represented by empty strings.

StringUtils.join(null, *) = null
StringUtils.join([], *) = ""
StringUtils.join([null], *) = ""
StringUtils.join(["a", "b", "c"], "--") = "a--b--c"
StringUtils.join(["a", "b", "c"], null) = "abc"
StringUtils.join(["a", "b", "c"], "") = "abc"
StringUtils.join([null, "", "a"], ',') = ",,a"

 public static String join(Iterator iterator,
    char separator) 
{
        // handle null, zero and one elements before building a buffer
        if (iterator == null) {
            return null;
        }
        if (!iterator.hasNext()) {
            return EMPTY;
        }
        Object first = iterator.next();
        if (!iterator.hasNext()) {
            return ObjectUtils.toString(first);
        }
        // two or more elements
        StringBuffer buf = new StringBuffer(256); // Java default is 16, probably too small
        if (first != null) {
            buf.append(first);
        }
        while (iterator.hasNext()) {
            buf.append(separator);
            Object obj = iterator.next();
            if (obj != null) {
                buf.append(obj);
            }
        }
        return buf.toString();
}

Joins the elements of the provided Iterator into a single String containing the provided elements.

No delimiter is added before or after the list. Null objects or empty strings within the iteration are represented by empty strings.

See the examples here: #join(Object[],char) .

 public static String join(Iterator iterator,
    String separator) 
{
        // handle null, zero and one elements before building a buffer
        if (iterator == null) {
            return null;
        }
        if (!iterator.hasNext()) {
            return EMPTY;
        }
        Object first = iterator.next();
        if (!iterator.hasNext()) {
            return ObjectUtils.toString(first);
        }
        // two or more elements
        StringBuffer buf = new StringBuffer(256); // Java default is 16, probably too small
        if (first != null) {
            buf.append(first);
        }
        while (iterator.hasNext()) {
            if (separator != null) {
                buf.append(separator);
            }
            Object obj = iterator.next();
            if (obj != null) {
                buf.append(obj);
            }
        }
        return buf.toString();
}

Joins the elements of the provided Iterator into a single String containing the provided elements.

No delimiter is added before or after the list. A null separator is the same as an empty String ("").

See the examples here: #join(Object[],String) .

 public static String join(Collection collection,
    char separator) 
{
        if (collection == null) {
            return null;
        }
        return join(collection.iterator(), separator);
}

Joins the elements of the provided Collection into a single String containing the provided elements.

No delimiter is added before or after the list. Null objects or empty strings within the iteration are represented by empty strings.

See the examples here: #join(Object[],char) .

 public static String join(Collection collection,
    String separator) 
{
        if (collection == null) {
            return null;
        }
        return join(collection.iterator(), separator);
}

Joins the elements of the provided Collection into a single String containing the provided elements.

No delimiter is added before or after the list. A null separator is the same as an empty String ("").

See the examples here: #join(Object[],String) .

 public static String join(Object[] array,
    char separator,
    int startIndex,
    int endIndex) 
{
        if (array == null) {
            return null;
        }
        int bufSize = (endIndex - startIndex);
        if (bufSize < = 0) {
            return EMPTY;
        }
        bufSize *= ((array[startIndex] == null ? 16 : array[startIndex].toString().length()) + 1);
        StringBuffer buf = new StringBuffer(bufSize);
        for (int i = startIndex; i <  endIndex; i++) {
            if (i  > startIndex) {
                buf.append(separator);
            }
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
}

Joins the elements of the provided array into a single String containing the provided list of elements.

No delimiter is added before or after the list. Null objects or empty strings within the array are represented by empty strings.

StringUtils.join(null, *) = null
StringUtils.join([], *) = ""
StringUtils.join([null], *) = ""
StringUtils.join(["a", "b", "c"], ';') = "a;b;c"
StringUtils.join(["a", "b", "c"], null) = "abc"
StringUtils.join([null, "", "a"], ';') = ";;a"

 public static String join(Object[] array,
    String separator,
    int startIndex,
    int endIndex) 
{
        if (array == null) {
            return null;
        }
        if (separator == null) {
            separator = EMPTY;
        }
        // endIndex - startIndex  > 0:   Len = NofStrings *(len(firstString) + len(separator))
        //           (Assuming that all Strings are roughly equally long)
        int bufSize = (endIndex - startIndex);
        if (bufSize < = 0) {
            return EMPTY;
        }
        bufSize *= ((array[startIndex] == null ? 16 : array[startIndex].toString().length())
                        + separator.length());
        StringBuffer buf = new StringBuffer(bufSize);
        for (int i = startIndex; i <  endIndex; i++) {
            if (i  > startIndex) {
                buf.append(separator);
            }
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
}

Joins the elements of the provided array into a single String containing the provided list of elements.

No delimiter is added before or after the list. A null separator is the same as an empty String (""). Null objects or empty strings within the array are represented by empty strings.

StringUtils.join(null, *) = null
StringUtils.join([], *) = ""
StringUtils.join([null], *) = ""
StringUtils.join(["a", "b", "c"], "--") = "a--b--c"
StringUtils.join(["a", "b", "c"], null) = "abc"
StringUtils.join(["a", "b", "c"], "") = "abc"
StringUtils.join([null, "", "a"], ',') = ",,a"

 public static int lastIndexOf(String str,
    char searchChar) 
{
        if (isEmpty(str)) {
            return -1;
        }
        return str.lastIndexOf(searchChar);
}

Finds the last index within a String, handling null. This method uses String#lastIndexOf(int) .

A null or empty ("") String will return -1.

StringUtils.lastIndexOf(null, *) = -1
StringUtils.lastIndexOf("", *) = -1
StringUtils.lastIndexOf("aabaabaa", 'a') = 7
StringUtils.lastIndexOf("aabaabaa", 'b') = 5

 public static int lastIndexOf(String str,
    String searchStr) 
{
        if (str == null || searchStr == null) {
            return -1;
        }
        return str.lastIndexOf(searchStr);
}

Finds the last index within a String, handling null. This method uses String#lastIndexOf(String) .

A null String will return -1.

StringUtils.lastIndexOf(null, *) = -1
StringUtils.lastIndexOf(*, null) = -1
StringUtils.lastIndexOf("", "") = 0
StringUtils.lastIndexOf("aabaabaa", "a") = 0
StringUtils.lastIndexOf("aabaabaa", "b") = 2
StringUtils.lastIndexOf("aabaabaa", "ab") = 1
StringUtils.lastIndexOf("aabaabaa", "") = 8

 public static int lastIndexOf(String str,
    char searchChar,
    int startPos) 
{
        if (isEmpty(str)) {
            return -1;
        }
        return str.lastIndexOf(searchChar, startPos);
}

Finds the last index within a String from a start position, handling null. This method uses String#lastIndexOf(int, int) .

A null or empty ("") String will return -1. A negative start position returns -1. A start position greater than the string length searches the whole string.

StringUtils.lastIndexOf(null, *, *) = -1
StringUtils.lastIndexOf("", *, *) = -1
StringUtils.lastIndexOf("aabaabaa", 'b', 8) = 5
StringUtils.lastIndexOf("aabaabaa", 'b', 4) = 2
StringUtils.lastIndexOf("aabaabaa", 'b', 0) = -1
StringUtils.lastIndexOf("aabaabaa", 'b', 9) = 5
StringUtils.lastIndexOf("aabaabaa", 'b', -1) = -1
StringUtils.lastIndexOf("aabaabaa", 'a', 0) = 0

 public static int lastIndexOf(String str,
    String searchStr,
    int startPos) 
{
        if (str == null || searchStr == null) {
            return -1;
        }
        return str.lastIndexOf(searchStr, startPos);
}

Finds the first index within a String, handling null. This method uses String#lastIndexOf(String, int) .

A null String will return -1. A negative start position returns -1. An empty ("") search String always matches unless the start position is negative. A start position greater than the string length searches the whole string.

StringUtils.lastIndexOf(null, *, *) = -1
StringUtils.lastIndexOf(*, null, *) = -1
StringUtils.lastIndexOf("aabaabaa", "a", 8) = 7
StringUtils.lastIndexOf("aabaabaa", "b", 8) = 5
StringUtils.lastIndexOf("aabaabaa", "ab", 8) = 4
StringUtils.lastIndexOf("aabaabaa", "b", 9) = 5
StringUtils.lastIndexOf("aabaabaa", "b", -1) = -1
StringUtils.lastIndexOf("aabaabaa", "a", 0) = 0
StringUtils.lastIndexOf("aabaabaa", "b", 0) = -1

 public static int lastIndexOfAny(String str,
    String[] searchStrs) 
{
        if ((str == null) || (searchStrs == null)) {
            return -1;
        }
        int sz = searchStrs.length;
        int ret = -1;
        int tmp = 0;
        for (int i = 0; i <  sz; i++) {
            String search = searchStrs[i];
            if (search == null) {
                continue;
            }
            tmp = str.lastIndexOf(search);
            if (tmp  > ret) {
                ret = tmp;
            }
        }
        return ret;
}

Find the latest index of any of a set of potential substrings.

A null String will return -1. A null search array will return -1. A null or zero length search array entry will be ignored, but a search array containing "" will return the length of str if str is not null. This method uses String#indexOf(String)

StringUtils.lastIndexOfAny(null, *) = -1
StringUtils.lastIndexOfAny(*, null) = -1
StringUtils.lastIndexOfAny(*, []) = -1
StringUtils.lastIndexOfAny(*, [null]) = -1
StringUtils.lastIndexOfAny("zzabyycdxx", ["ab","cd"]) = 6
StringUtils.lastIndexOfAny("zzabyycdxx", ["cd","ab"]) = 6
StringUtils.lastIndexOfAny("zzabyycdxx", ["mn","op"]) = -1
StringUtils.lastIndexOfAny("zzabyycdxx", ["mn","op"]) = -1
StringUtils.lastIndexOfAny("zzabyycdxx", ["mn",""]) = 10

 public static String left(String str,
    int len) 
{
        if (str == null) {
            return null;
        }
        if (len <  0) {
            return EMPTY;
        }
        if (str.length() < = len) {
            return str;
        }
        return str.substring(0, len);
}

Gets the leftmost len characters of a String.

If len characters are not available, or the String is null, the String will be returned without an exception. An exception is thrown if len is negative.

StringUtils.left(null, *) = null
StringUtils.left(*, -ve) = ""
StringUtils.left("", *) = ""
StringUtils.left("abc", 0) = ""
StringUtils.left("abc", 2) = "ab"
StringUtils.left("abc", 4) = "abc"

 public static String leftPad(String str,
    int size) 
{
        return leftPad(str, size, ' ");
}

Left pad a String with spaces (' ').

The String is padded to the size of size.

StringUtils.leftPad(null, *) = null
StringUtils.leftPad("", 3) = " "
StringUtils.leftPad("bat", 3) = "bat"
StringUtils.leftPad("bat", 5) = " bat"
StringUtils.leftPad("bat", 1) = "bat"
StringUtils.leftPad("bat", -1) = "bat"

 public static String leftPad(String str,
    int size,
    char padChar) 
{
        if (str == null) {
            return null;
        }
        int pads = size - str.length();
        if (pads < = 0) {
            return str; // returns original String when possible
        }
        if (pads  > PAD_LIMIT) {
            return leftPad(str, size, String.valueOf(padChar));
        }
        return padding(pads, padChar).concat(str);
}

Left pad a String with a specified character.

Pad to a size of size.

StringUtils.leftPad(null, *, *) = null
StringUtils.leftPad("", 3, 'z') = "zzz"
StringUtils.leftPad("bat", 3, 'z') = "bat"
StringUtils.leftPad("bat", 5, 'z') = "zzbat"
StringUtils.leftPad("bat", 1, 'z') = "bat"
StringUtils.leftPad("bat", -1, 'z') = "bat"

 public static String leftPad(String str,
    int size,
    String padStr) 
{
        if (str == null) {
            return null;
        }
        if (isEmpty(padStr)) {
            padStr = " ";
        }
        int padLen = padStr.length();
        int strLen = str.length();
        int pads = size - strLen;
        if (pads < = 0) {
            return str; // returns original St