StackTraceElement.java revision 14138:0dfea12d7199
1/* 2 * Copyright (c) 2000, 2016, 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 26package java.lang; 27 28import 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 */ 42public final class StackTraceElement implements java.io.Serializable { 43 // Normally initialized by VM (public constructor added in 1.5) 44 private String moduleName; 45 private String moduleVersion; 46 private String declaringClass; 47 private String methodName; 48 private String fileName; 49 private int lineNumber; 50 51 /** 52 * Creates a stack trace element representing the specified execution 53 * point. The {@link #getModuleName module name} and {@link 54 * #getModuleVersion module version} of the stack trace element will 55 * be {@code null}. 56 * 57 * @param declaringClass the fully qualified name of the class containing 58 * the execution point represented by the stack trace element 59 * @param methodName the name of the method containing the execution point 60 * represented by the stack trace element 61 * @param fileName the name of the file containing the execution point 62 * represented by the stack trace element, or {@code null} if 63 * this information is unavailable 64 * @param lineNumber the line number of the source line containing the 65 * execution point represented by this stack trace element, or 66 * a negative number if this information is unavailable. A value 67 * of -2 indicates that the method containing the execution point 68 * is a native method 69 * @throws NullPointerException if {@code declaringClass} or 70 * {@code methodName} is null 71 * @since 1.5 72 */ 73 public StackTraceElement(String declaringClass, String methodName, 74 String fileName, int lineNumber) { 75 this(null, null, declaringClass, methodName, fileName, lineNumber); 76 } 77 78 /** 79 * Creates a stack trace element representing the specified execution 80 * point. 81 * 82 * @param moduleName the module name if the class containing the 83 * execution point represented by the stack trace is in a named 84 * module; can be {@code null} 85 * @param moduleVersion the module version if the class containing the 86 * execution point represented by the stack trace is in a named 87 * module that has a version; can be {@code null} 88 * @param declaringClass the fully qualified name of the class containing 89 * the execution point represented by the stack trace element 90 * @param methodName the name of the method containing the execution point 91 * represented by the stack trace element 92 * @param fileName the name of the file containing the execution point 93 * represented by the stack trace element, or {@code null} if 94 * this information is unavailable 95 * @param lineNumber the line number of the source line containing the 96 * execution point represented by this stack trace element, or 97 * a negative number if this information is unavailable. A value 98 * of -2 indicates that the method containing the execution point 99 * is a native method 100 * @throws NullPointerException if {@code declaringClass} is {@code null} 101 * or {@code methodName} is {@code null} 102 * @since 9 103 */ 104 public StackTraceElement(String moduleName, String moduleVersion, 105 String declaringClass, String methodName, 106 String fileName, int lineNumber) { 107 this.moduleName = moduleName; 108 this.moduleVersion = moduleVersion; 109 this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null"); 110 this.methodName = Objects.requireNonNull(methodName, "Method name is null"); 111 this.fileName = fileName; 112 this.lineNumber = lineNumber; 113 } 114 115 116 /** 117 * Creates an empty stack frame element to be filled in by Throwable. 118 */ 119 StackTraceElement() { } 120 121 /** 122 * Returns the name of the source file containing the execution point 123 * represented by this stack trace element. Generally, this corresponds 124 * to the {@code SourceFile} attribute of the relevant {@code class} 125 * file (as per <i>The Java Virtual Machine Specification</i>, Section 126 * 4.7.7). In some systems, the name may refer to some source code unit 127 * other than a file, such as an entry in source repository. 128 * 129 * @return the name of the file containing the execution point 130 * represented by this stack trace element, or {@code null} if 131 * this information is unavailable. 132 */ 133 public String getFileName() { 134 return fileName; 135 } 136 137 /** 138 * Returns the line number of the source line containing the execution 139 * point represented by this stack trace element. Generally, this is 140 * derived from the {@code LineNumberTable} attribute of the relevant 141 * {@code class} file (as per <i>The Java Virtual Machine 142 * Specification</i>, Section 4.7.8). 143 * 144 * @return the line number of the source line containing the execution 145 * point represented by this stack trace element, or a negative 146 * number if this information is unavailable. 147 */ 148 public int getLineNumber() { 149 return lineNumber; 150 } 151 152 /** 153 * Returns the module name of the module containing the execution point 154 * represented by this stack trace element. 155 * 156 * @return the module name of the {@code Module} containing the execution 157 * point represented by this stack trace element; {@code null} 158 * if the module name is not available. 159 * @since 9 160 * @see java.lang.reflect.Module#getName() 161 */ 162 public String getModuleName() { 163 return moduleName; 164 } 165 166 /** 167 * Returns the module version of the module containing the execution point 168 * represented by this stack trace element. 169 * 170 * @return the module version of the {@code Module} containing the execution 171 * point represented by this stack trace element; {@code null} 172 * if the module version is not available. 173 * @since 9 174 * @see java.lang.module.ModuleDescriptor.Version 175 */ 176 public String getModuleVersion() { 177 return moduleVersion; 178 } 179 180 /** 181 * Returns the fully qualified name of the class containing the 182 * execution point represented by this stack trace element. 183 * 184 * @return the fully qualified name of the {@code Class} containing 185 * the execution point represented by this stack trace element. 186 */ 187 public String getClassName() { 188 return declaringClass; 189 } 190 191 /** 192 * Returns the name of the method containing the execution point 193 * represented by this stack trace element. If the execution point is 194 * contained in an instance or class initializer, this method will return 195 * the appropriate <i>special method name</i>, {@code <init>} or 196 * {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual 197 * Machine Specification</i>. 198 * 199 * @return the name of the method containing the execution point 200 * represented by this stack trace element. 201 */ 202 public String getMethodName() { 203 return methodName; 204 } 205 206 /** 207 * Returns true if the method containing the execution point 208 * represented by this stack trace element is a native method. 209 * 210 * @return {@code true} if the method containing the execution point 211 * represented by this stack trace element is a native method. 212 */ 213 public boolean isNativeMethod() { 214 return lineNumber == -2; 215 } 216 217 /** 218 * Returns a string representation of this stack trace element. The 219 * format of this string depends on the implementation, but the following 220 * examples may be regarded as typical: 221 * <ul> 222 * <li> 223 * {@code "MyClass.mash(my.module@9.0/MyClass.java:101)"} - Here, 224 * {@code "MyClass"} is the <i>fully-qualified name</i> of the class 225 * containing the execution point represented by this stack trace element, 226 * {@code "mash"} is the name of the method containing the execution 227 * point, {@code "my.module"} is the module name, {@code "9.0"} is the 228 * module version, and {@code "101"} is the line number of the source 229 * line containing the execution point. 230 * <li> 231 * {@code "MyClass.mash(my.module@9.0/MyClass.java)"} - As above, but the 232 * line number is unavailable. 233 * <li> 234 * {@code "MyClass.mash(my.module@9.0/Unknown Source)"} - As above, but 235 * neither the file name nor the line number are available. 236 * <li> 237 * {@code "MyClass.mash(my.module@9.0/Native Method)"} - As above, but 238 * neither the file name nor the line number are available, and the 239 * method containing the execution point is known to be a native method. 240 * </ul> 241 * If the execution point is not in a named module, {@code "my.module@9.0/"} 242 * will be omitted from the above. 243 * 244 * @see Throwable#printStackTrace() 245 */ 246 public String toString() { 247 String mid = ""; 248 if (moduleName != null) { 249 mid = moduleName; 250 if (moduleVersion != null) 251 mid += "@" + moduleVersion; 252 mid += "/"; 253 } 254 return getClassName() + "." + methodName + "(" + mid + 255 (isNativeMethod() ? "Native Method)" : 256 (fileName != null && lineNumber >= 0 ? 257 fileName + ":" + lineNumber + ")" : 258 (fileName != null ? ""+fileName+")" : "Unknown Source)"))); 259 } 260 261 /** 262 * Returns true if the specified object is another 263 * {@code StackTraceElement} instance representing the same execution 264 * point as this instance. Two stack trace elements {@code a} and 265 * {@code b} are equal if and only if: 266 * <pre>{@code 267 * equals(a.getFileName(), b.getFileName()) && 268 * a.getLineNumber() == b.getLineNumber()) && 269 * equals(a.getModuleName(), b.getModuleName()) && 270 * equals(a.getModuleVersion(), b.getModuleVersion()) && 271 * equals(a.getClassName(), b.getClassName()) && 272 * equals(a.getMethodName(), b.getMethodName()) 273 * }</pre> 274 * where {@code equals} has the semantics of {@link 275 * java.util.Objects#equals(Object, Object) Objects.equals}. 276 * 277 * @param obj the object to be compared with this stack trace element. 278 * @return true if the specified object is another 279 * {@code StackTraceElement} instance representing the same 280 * execution point as this instance. 281 */ 282 public boolean equals(Object obj) { 283 if (obj==this) 284 return true; 285 if (!(obj instanceof StackTraceElement)) 286 return false; 287 StackTraceElement e = (StackTraceElement)obj; 288 return e.declaringClass.equals(declaringClass) && 289 Objects.equals(moduleName, e.moduleName) && 290 Objects.equals(moduleVersion, e.moduleVersion) && 291 e.lineNumber == lineNumber && 292 Objects.equals(methodName, e.methodName) && 293 Objects.equals(fileName, e.fileName); 294 } 295 296 /** 297 * Returns a hash code value for this stack trace element. 298 */ 299 public int hashCode() { 300 int result = 31*declaringClass.hashCode() + methodName.hashCode(); 301 result = 31*result + Objects.hashCode(moduleName); 302 result = 31*result + Objects.hashCode(moduleVersion); 303 result = 31*result + Objects.hashCode(fileName); 304 result = 31*result + lineNumber; 305 return result; 306 } 307 308 private static final long serialVersionUID = 6992337162326171013L; 309} 310