/*
 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package java.lang;

import java.util.Objects;

/**
 * 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 {@code 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 {@code declaringClass} or
 * {@code methodName} is null
 * @since 1.5
 */
 public StackTraceElement(String declaringClass, String methodName,
 String fileName, int lineNumber) {
 this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null");
 this.methodName = Objects.requireNonNull(methodName, "Method name is null");
 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 {@code SourceFile} attribute of the relevant {@code class}
 * file (as per <i>The Java Virtual Machine Specification</i>, 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 {@code 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 {@code LineNumberTable} attribute of the relevant
 * {@code class} file (as per <i>The Java Virtual Machine
 * Specification</i>, 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 {@code 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 <i>special method name</i>, {@code <init>} or
 * {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual
 * Machine Specification</i>.
 *
 * @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 {@code 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:
 * <ul>
 * <li>
 * {@code "MyClass.mash(MyClass.java:9)"} - Here, {@code "MyClass"}
 * is the <i>fully-qualified name</i> of the class containing the
 * execution point represented by this stack trace element,
 * {@code "mash"} is the name of the method containing the execution
 * point, {@code "MyClass.java"} is the source file containing the
 * execution point, and {@code "9"} is the line number of the source
 * line containing the execution point.
 * <li>
 * {@code "MyClass.mash(MyClass.java)"} - As above, but the line
 * number is unavailable.
 * <li>
 * {@code "MyClass.mash(Unknown Source)"} - As above, but neither
 * the file name nor the line number are available.
 * <li>
 * {@code "MyClass.mash(Native Method)"} - As above, but neither
 * the file name nor the line number are available, and the method
 * containing the execution point is known to be a native method.
 * </ul>
 * @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
 * {@code StackTraceElement} instance representing the same execution
 * point as this instance. Two stack trace elements {@code a} and
 * {@code b} are equal if and only if:
 * <pre>{@code
 * equals(a.getFileName(), b.getFileName()) &&
 * a.getLineNumber() == b.getLineNumber()) &&
 * equals(a.getClassName(), b.getClassName()) &&
 * equals(a.getMethodName(), b.getMethodName())
 * }</pre>
 * where {@code equals} has the semantics of {@link
 * java.util.Objects#equals(Object, Object) Objects.equals}.
 *
 * @param obj the object to be compared with this stack trace element.
 * @return true if the specified object is another
 * {@code 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 &&
 Objects.equals(methodName, e.methodName) &&
 Objects.equals(fileName, e.fileName);
 }

 /**
 * Returns a hash code value for this stack trace element.
 */
 public int hashCode() {
 int result = 31*declaringClass.hashCode() + methodName.hashCode();
 result = 31*result + Objects.hashCode(fileName);
 result = 31*result + lineNumber;
 return result;
 }

 private static final long serialVersionUID = 6992337162326171013L;
}