Source code: javatools/util/NullUtils.java
1 /*
2 * NullUtils.java
3 *
4 * Created on 20 febbraio 2002, 18.08
5 Javatools (modified version) - Some useful general classes.
6 Copyright (C) 2002-2003 Chris Bitmead (original) Antonio Petrelli (modified)
7
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2 of the License, or
11 (at your option) any later version.
12
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
17
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21
22 Contact me at: brenmcguire@users.sourceforge.net
23 */
24
25 package javatools.util;
26
27 import java.util.List;
28 import java.util.ArrayList;
29 import java.util.Iterator;
30
31 /**
32 * Contains some functions for use with null values.
33 * @author Antonio Petrelli
34 * @version 0.0.1
35 */
36 public class NullUtils {
37
38 /** Creates new NullUtils */
39 public NullUtils() {
40 }
41
42 /** Returns an array of null objects.
43 * @param count How many objects in the array?
44 * @return The requested array.
45 */
46 public static Object[] nullArray(int count) {
47 int i;
48 Object[] response;
49
50 if (count > 0) {
51 response = new Object[count];
52 for (i=0; i < count; i++)
53 response[i] = null;
54 }
55 else
56 response = null;
57 return response;
58 }
59
60 /** A List of null objects.
61 * @param count How many objects do you want?
62 * @return The requested list.
63 */
64 public static List nullList(int count) {
65 int i;
66 List response;
67
68 if (count > 0) {
69 response = new ArrayList();
70 for (i=0; i < count; i++)
71 response.add(null);
72 }
73 else
74 response = null;
75 return response;
76 }
77
78 /** Checks if an array is made only of null objects.
79 * @param arr The array to check.
80 * @return <CODE>true</CODE>: the array contains only null objects;
81 * <CODE>false</CODE>: otherwise.
82 */
83 public static boolean isArrayNull(Object[] arr) {
84 int i, numObjects;
85 boolean response;
86
87 numObjects = arr.length;
88 response = true;
89 for (i=0; i < numObjects && response; i++)
90 if (arr[i] != null)
91 response = false;
92 return response;
93 }
94
95 /** Checks if a list contains only null objects.
96 * @param lst The list to check.
97 * @return <CODE>true</CODE>: the list contains only null objects;
98 * <CODE>false</CODE>: otherwise.
99 */
100 public static boolean isListNull(List lst) {
101 Iterator it;
102 boolean response;
103
104 it = lst.iterator();
105 response = true;
106 while (it.hasNext() && response)
107 if (it.next() != null)
108 response = false;
109 return response;
110 }
111 }