/* * @(#)StackTraceElement.java 1.10 04/02/19 * * Copyright 2004 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.lang; /** * An element in a stack trace, as returned by {@link * Throwable#getStackTrace()}. Each element represents a single stack frame. * All stack frames except for the one at the top of the stack represent * a method invocation. The frame at the top of the stack represents the * execution point at which the stack trace was generated. Typically, * this is the point at which the throwable corresponding to the stack trace * was created. * * @since 1.4 * @author Josh Bloch */ public final class StackTraceElement implements java.io.Serializable { // Normally initialized by VM (public constructor added in 1.5) private String declaringClass; private String methodName; private String fileName; private int lineNumber; /** * Creates a stack trace element representing the specified execution * point. * * @param declaringClass the fully qualified name of the class containing * the execution point represented by the stack trace element * @param methodName the name of the method containing the execution point * represented by the stack trace element * @param fileName the name of the file containing the execution point * represented by the stack trace element, or null if * this information is unavailable * @param lineNumber the line number of the source line containing the * execution point represented by this stack trace element, or * a negative number if this information is unavailable. A value * of -2 indicates that the method containing the execution point * is a native method * @throws NullPointerException if declaringClass or * methodName is null * @since 1.5 */ public StackTraceElement(String declaringClass, String methodName, String fileName, int lineNumber) { if (declaringClass == null) throw new NullPointerException("Declaring class is null"); if (methodName == null) throw new NullPointerException("Method name is null"); this.declaringClass = declaringClass; this.methodName = methodName; this.fileName = fileName; this.lineNumber = lineNumber; } /** * Returns the name of the source file containing the execution point * represented by this stack trace element. Generally, this corresponds * to the SourceFile attribute of the relevant class * file (as per The Java Virtual Machine Specification, Section * 4.7.7). In some systems, the name may refer to some source code unit * other than a file, such as an entry in source repository. * * @return the name of the file containing the execution point * represented by this stack trace element, or null if * this information is unavailable. */ public String getFileName() { return fileName; } /** * Returns the line number of the source line containing the execution * point represented by this stack trace element. Generally, this is * derived from the LineNumberTable attribute of the relevant * class file (as per The Java Virtual Machine * Specification, Section 4.7.8). * * @return the line number of the source line containing the execution * point represented by this stack trace element, or a negative * number if this information is unavailable. */ public int getLineNumber() { return lineNumber; } /** * Returns the fully qualified name of the class containing the * execution point represented by this stack trace element. * * @return the fully qualified name of the Class containing * the execution point represented by this stack trace element. */ public String getClassName() { return declaringClass; } /** * Returns the name of the method containing the execution point * represented by this stack trace element. If the execution point is * contained in an instance or class initializer, this method will return * the appropriate special method name, <init> or * <clinit>, as per Section 3.9 of The Java Virtual * Machine Specification. * * @return the name of the method containing the execution point * represented by this stack trace element. */ public String getMethodName() { return methodName; } /** * Returns true if the method containing the execution point * represented by this stack trace element is a native method. * * @return true if the method containing the execution point * represented by this stack trace element is a native method. */ public boolean isNativeMethod() { return lineNumber == -2; } /** * Returns a string representation of this stack trace element. The * format of this string depends on the implementation, but the following * examples may be regarded as typical: * * @see Throwable#printStackTrace() */ public String toString() { return getClassName() + "." + methodName + (isNativeMethod() ? "(Native Method)" : (fileName != null && lineNumber >= 0 ? "(" + fileName + ":" + lineNumber + ")" : (fileName != null ? "("+fileName+")" : "(Unknown Source)"))); } /** * Returns true if the specified object is another * StackTraceElement instance representing the same execution * point as this instance. Two stack trace elements a and * b are equal if and only if: * 
     *     equals(a.getFileName(), b.getFileName()) &&
     *     a.getLineNumber() == b.getLineNumber()) &&
     *     equals(a.getClassName(), b.getClassName()) &&
     *     equals(a.getMethodName(), b.getMethodName())
     *
* where equals is defined as: * 
     *     static boolean equals(Object a, Object b) {
     *         return a==b || (a != null && a.equals(b));
     *     }
     *
* * @param obj the object to be compared with this stack trace element. * @return true if the specified object is another * StackTraceElement instance representing the same * execution point as this instance. */ public boolean equals(Object obj) { if (obj==this) return true; if (!(obj instanceof StackTraceElement)) return false; StackTraceElement e = (StackTraceElement)obj; return e.declaringClass.equals(declaringClass) && e.lineNumber == lineNumber && eq(methodName, e.methodName) && eq(fileName, e.fileName); } private static boolean eq(Object a, Object b) { return a==b || (a != null && a.equals(b)); } /** * Returns a hash code value for this stack trace element. */ public int hashCode() { int result = 31*declaringClass.hashCode() + methodName.hashCode(); result = 31*result + (fileName == null ? 0 : fileName.hashCode()); result = 31*result + lineNumber; return result; } private static final long serialVersionUID = 6992337162326171013L; }