1 /* 2 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.lang; 27 28 import java.util.Objects; 29 30 /** 31 * An element in a stack trace, as returned by {@link 32 * Throwable#getStackTrace()}. Each element represents a single stack frame. 33 * All stack frames except for the one at the top of the stack represent 34 * a method invocation. The frame at the top of the stack represents the 35 * execution point at which the stack trace was generated. Typically, 36 * this is the point at which the throwable corresponding to the stack trace 37 * was created. 38 * 39 * @since 1.4 40 * @author Josh Bloch 41 */ 42 public final class StackTraceElement implements java.io.Serializable { 43 // Normally initialized by VM (public constructor added in 1.5) 44 private String declaringClass; 45 private String methodName; 46 private String fileName; 47 private int lineNumber; 48 49 /** 50 * Creates a stack trace element representing the specified execution 51 * point. 52 * 53 * @param declaringClass the fully qualified name of the class containing 54 * the execution point represented by the stack trace element 55 * @param methodName the name of the method containing the execution point 56 * represented by the stack trace element 57 * @param fileName the name of the file containing the execution point 58 * represented by the stack trace element, or {@code null} if 59 * this information is unavailable 60 * @param lineNumber the line number of the source line containing the 61 * execution point represented by this stack trace element, or 62 * a negative number if this information is unavailable. A value 63 * of -2 indicates that the method containing the execution point 64 * is a native method 65 * @throws NullPointerException if {@code declaringClass} or 66 * {@code methodName} is null 67 * @since 1.5 68 */ 69 public StackTraceElement(String declaringClass, String methodName, 70 String fileName, int lineNumber) { 71 this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null"); 72 this.methodName = Objects.requireNonNull(methodName, "Method name is null"); 73 this.fileName = fileName; 74 this.lineNumber = lineNumber; 75 } 76 77 78 /** 79 * Creates an empty stack frame element to be filled in by Throwable. 80 * @since 1.9 81 */ 82 StackTraceElement() { } 83 84 /** 85 * Returns the name of the source file containing the execution point 86 * represented by this stack trace element. Generally, this corresponds 87 * to the {@code SourceFile} attribute of the relevant {@code class} 88 * file (as per <i>The Java Virtual Machine Specification</i>, Section 89 * 4.7.7). In some systems, the name may refer to some source code unit 90 * other than a file, such as an entry in source repository. 91 * 92 * @return the name of the file containing the execution point 93 * represented by this stack trace element, or {@code null} if 94 * this information is unavailable. 95 */ 96 public String getFileName() { 97 return fileName; 98 } 99 100 /** 101 * Returns the line number of the source line containing the execution 102 * point represented by this stack trace element. Generally, this is 103 * derived from the {@code LineNumberTable} attribute of the relevant 104 * {@code class} file (as per <i>The Java Virtual Machine 105 * Specification</i>, Section 4.7.8). 106 * 107 * @return the line number of the source line containing the execution 108 * point represented by this stack trace element, or a negative 109 * number if this information is unavailable. 110 */ 111 public int getLineNumber() { 112 return lineNumber; 113 } 114 115 /** 116 * Returns the fully qualified name of the class containing the 117 * execution point represented by this stack trace element. 118 * 119 * @return the fully qualified name of the {@code Class} containing 120 * the execution point represented by this stack trace element. 121 */ 122 public String getClassName() { 123 return declaringClass; 124 } 125 126 /** 127 * Returns the name of the method containing the execution point 128 * represented by this stack trace element. If the execution point is 129 * contained in an instance or class initializer, this method will return 130 * the appropriate <i>special method name</i>, {@code <init>} or 131 * {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual 132 * Machine Specification</i>. 133 * 134 * @return the name of the method containing the execution point 135 * represented by this stack trace element. 136 */ 137 public String getMethodName() { 138 return methodName; 139 } 140 141 /** 142 * Returns true if the method containing the execution point 143 * represented by this stack trace element is a native method. 144 * 145 * @return {@code true} if the method containing the execution point 146 * represented by this stack trace element is a native method. 147 */ 148 public boolean isNativeMethod() { 149 return lineNumber == -2; 150 } 151 152 /** 153 * Returns a string representation of this stack trace element. The 154 * format of this string depends on the implementation, but the following 155 * examples may be regarded as typical: 156 * <ul> 157 * <li> 158 * {@code "MyClass.mash(MyClass.java:9)"} - Here, {@code "MyClass"} 159 * is the <i>fully-qualified name</i> of the class containing the 160 * execution point represented by this stack trace element, 161 * {@code "mash"} is the name of the method containing the execution 162 * point, {@code "MyClass.java"} is the source file containing the 163 * execution point, and {@code "9"} is the line number of the source 164 * line containing the execution point. 165 * <li> 166 * {@code "MyClass.mash(MyClass.java)"} - As above, but the line 167 * number is unavailable. 168 * <li> 169 * {@code "MyClass.mash(Unknown Source)"} - As above, but neither 170 * the file name nor the line number are available. 171 * <li> 172 * {@code "MyClass.mash(Native Method)"} - As above, but neither 173 * the file name nor the line number are available, and the method 174 * containing the execution point is known to be a native method. 175 * </ul> 176 * @see Throwable#printStackTrace() 177 */ 178 public String toString() { 179 return getClassName() + "." + methodName + 180 (isNativeMethod() ? "(Native Method)" : 181 (fileName != null && lineNumber >= 0 ? 182 "(" + fileName + ":" + lineNumber + ")" : 183 (fileName != null ? "("+fileName+")" : "(Unknown Source)"))); 184 } 185 186 /** 187 * Returns true if the specified object is another 188 * {@code StackTraceElement} instance representing the same execution 189 * point as this instance. Two stack trace elements {@code a} and 190 * {@code b} are equal if and only if: 191 * <pre>{@code 192 * equals(a.getFileName(), b.getFileName()) && 193 * a.getLineNumber() == b.getLineNumber()) && 194 * equals(a.getClassName(), b.getClassName()) && 195 * equals(a.getMethodName(), b.getMethodName()) 196 * }</pre> 197 * where {@code equals} has the semantics of {@link 198 * java.util.Objects#equals(Object, Object) Objects.equals}. 199 * 200 * @param obj the object to be compared with this stack trace element. 201 * @return true if the specified object is another 202 * {@code StackTraceElement} 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) && 212 e.lineNumber == lineNumber && 213 Objects.equals(methodName, e.methodName) && 214 Objects.equals(fileName, e.fileName); 215 } 216 217 /** 218 * Returns a hash code value for this stack trace element. 219 */ 220 public int hashCode() { 221 int result = 31*declaringClass.hashCode() + methodName.hashCode(); 222 result = 31*result + Objects.hashCode(fileName); 223 result = 31*result + lineNumber; 224 return result; 225 } 226 227 private static final long serialVersionUID = 6992337162326171013L; 228 } --- EOF ---