1 /*
2 * Copyright 2000-2004 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.lang;
27
28 /**
29 * An element in a stack trace, as returned by {@link
30 * Throwable#getStackTrace()}. Each element represents a single stack frame.
31 * All stack frames except for the one at the top of the stack represent
32 * a method invocation. The frame at the top of the stack represents the
33 * execution point at which the stack trace was generated. Typically,
34 * this is the point at which the throwable corresponding to the stack trace
35 * was created.
36 *
37 * @since 1.4
38 * @author Josh Bloch
39 */
40 public final class StackTraceElement implements java.io.Serializable {
41 // Normally initialized by VM (public constructor added in 1.5)
42 private String declaringClass;
43 private String methodName;
44 private String fileName;
45 private int lineNumber;
46
47 /**
48 * Creates a stack trace element representing the specified execution
49 * point.
50 *
51 * @param declaringClass the fully qualified name of the class containing
52 * the execution point represented by the stack trace element
53 * @param methodName the name of the method containing the execution point
54 * represented by the stack trace element
55 * @param fileName the name of the file containing the execution point
56 * represented by the stack trace element, or <tt>null</tt> if
57 * this information is unavailable
58 * @param lineNumber the line number of the source line containing the
59 * execution point represented by this stack trace element, or
60 * a negative number if this information is unavailable. A value
61 * of -2 indicates that the method containing the execution point
62 * is a native method
63 * @throws NullPointerException if <tt>declaringClass</tt> or
64 * <tt>methodName</tt> is null
65 * @since 1.5
66 */
67 public StackTraceElement(String declaringClass, String methodName,
68 String fileName, int lineNumber) {
69 if (declaringClass == null)
70 throw new NullPointerException("Declaring class is null");
71 if (methodName == null)
72 throw new NullPointerException("Method name is null");
73
74 this.declaringClass = declaringClass;
75 this.methodName = methodName;
76 this.fileName = fileName;
77 this.lineNumber = lineNumber;
78 }
79
80 /**
81 * Returns the name of the source file containing the execution point
82 * represented by this stack trace element. Generally, this corresponds
83 * to the <tt>SourceFile</tt> attribute of the relevant <tt>class</tt>
84 * file (as per <i>The Java Virtual Machine Specification</i>, Section
85 * 4.7.7). In some systems, the name may refer to some source code unit
86 * other than a file, such as an entry in source repository.
87 *
88 * @return the name of the file containing the execution point
89 * represented by this stack trace element, or <tt>null</tt> if
90 * this information is unavailable.
91 */
92 public String getFileName() {
93 return fileName;
94 }
95
96 /**
97 * Returns the line number of the source line containing the execution
98 * point represented by this stack trace element. Generally, this is
99 * derived from the <tt>LineNumberTable</tt> attribute of the relevant
100 * <tt>class</tt> file (as per <i>The Java Virtual Machine
101 * Specification</i>, Section 4.7.8).
102 *
103 * @return the line number of the source line containing the execution
104 * point represented by this stack trace element, or a negative
105 * number if this information is unavailable.
106 */
107 public int getLineNumber() {
108 return lineNumber;
109 }
110
111 /**
112 * Returns the fully qualified name of the class containing the
113 * execution point represented by this stack trace element.
114 *
115 * @return the fully qualified name of the <tt>Class</tt> containing
116 * the execution point represented by this stack trace element.
117 */
118 public String getClassName() {
119 return declaringClass;
120 }
121
122 /**
123 * Returns the name of the method containing the execution point
124 * represented by this stack trace element. If the execution point is
125 * contained in an instance or class initializer, this method will return
126 * the appropriate <i>special method name</i>, <tt><init></tt> or
127 * <tt><clinit></tt>, as per Section 3.9 of <i>The Java Virtual
128 * Machine Specification</i>.
129 *
130 * @return the name of the method containing the execution point
131 * represented by this stack trace element.
132 */
133 public String getMethodName() {
134 return methodName;
135 }
136
137 /**
138 * Returns true if the method containing the execution point
139 * represented by this stack trace element is a native method.
140 *
141 * @return <tt>true</tt> if the method containing the execution point
142 * represented by this stack trace element is a native method.
143 */
144 public boolean isNativeMethod() {
145 return lineNumber == -2;
146 }
147
148 /**
149 * Returns a string representation of this stack trace element. The
150 * format of this string depends on the implementation, but the following
151 * examples may be regarded as typical:
152 * <ul>
153 * <li>
154 * <tt>"MyClass.mash(MyClass.java:9)"</tt> - Here, <tt>"MyClass"</tt>
155 * is the <i>fully-qualified name</i> of the class containing the
156 * execution point represented by this stack trace element,
157 * <tt>"mash"</tt> is the name of the method containing the execution
158 * point, <tt>"MyClass.java"</tt> is the source file containing the
159 * execution point, and <tt>"9"</tt> is the line number of the source
160 * line containing the execution point.
161 * <li>
162 * <tt>"MyClass.mash(MyClass.java)"</tt> - As above, but the line
163 * number is unavailable.
164 * <li>
165 * <tt>"MyClass.mash(Unknown Source)"</tt> - As above, but neither
166 * the file name nor the line number are available.
167 * <li>
168 * <tt>"MyClass.mash(Native Method)"</tt> - As above, but neither
169 * the file name nor the line number are available, and the method
170 * containing the execution point is known to be a native method.
171 * </ul>
172 * @see Throwable#printStackTrace()
173 */
174 public String toString() {
175 return getClassName() + "." + methodName +
176 (isNativeMethod() ? "(Native Method)" :
177 (fileName != null && lineNumber >= 0 ?
178 "(" + fileName + ":" + lineNumber + ")" :
179 (fileName != null ? "("+fileName+")" : "(Unknown Source)")));
180 }
181
182 /**
183 * Returns true if the specified object is another
184 * <tt>StackTraceElement</tt> instance representing the same execution
185 * point as this instance. Two stack trace elements <tt>a</tt> and
186 * <tt>b</tt> are equal if and only if:
187 * <pre>
188 * equals(a.getFileName(), b.getFileName()) &&
189 * a.getLineNumber() == b.getLineNumber()) &&
190 * equals(a.getClassName(), b.getClassName()) &&
191 * equals(a.getMethodName(), b.getMethodName())
192 * </pre>
193 * where <tt>equals</tt> is defined as:
194 * <pre>
195 * static boolean equals(Object a, Object b) {
196 * return a==b || (a != null && a.equals(b));
197 * }
198 * </pre>
199 *
200 * @param obj the object to be compared with this stack trace element.
201 * @return true if the specified object is another
202 * <tt>StackTraceElement</tt> instance representing the same
203 * execution point as this instance.
204 */
205 public boolean equals(Object obj) {
206 if (obj==this)
207 return true;
208 if (!(obj instanceof StackTraceElement))
209 return false;
210 StackTraceElement e = (StackTraceElement)obj;
211 return e.declaringClass.equals(declaringClass) && e.lineNumber == lineNumber
212 && eq(methodName, e.methodName) && eq(fileName, e.fileName);
213 }
214
215 private static boolean eq(Object a, Object b) {
216 return a==b || (a != null && a.equals(b));
217 }
218
219 /**
220 * Returns a hash code value for this stack trace element.
221 */
222 public int hashCode() {
223 int result = 31*declaringClass.hashCode() + methodName.hashCode();
224 result = 31*result + (fileName == null ? 0 : fileName.hashCode());
225 result = 31*result + lineNumber;
226 return result;
227 }
228
229 private static final long serialVersionUID = 6992337162326171013L;
230 }
Save This Page