content: /*
   * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  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() {
          // BEGIN Android-changed: Fall back Unknown Source:<dex_pc> for unknown lineNumber.
          // http://b/30183883
          // The only behavior change is that "Unknown Source" is followed by a number
          // (the value of the dex program counter, dex_pc), which never occurs on the
          // RI. This value isn't a line number, but can be useful for debugging and
          // avoids the need to ship line number information along with the dex code to
          // get an accurate stack trace.
          // Formatting it in this way might be more digestible to automated tools that
          // are not specifically written to expect this behavior.
          /*
          return getClassName() + "." + methodName +
              (isNativeMethod() ? "(Native Method)" :
               (fileName != null && lineNumber >= 0 ?
                "(" + fileName + ":" + lineNumber + ")" :
                (fileName != null ?  "("+fileName+")" : "(Unknown Source)")));
          */
          StringBuilder result = new StringBuilder();
          result.append(getClassName()).append(".").append(methodName);
          if (isNativeMethod()) {
              result.append("(Native Method)");
          } else if (fileName != null) {
              if (lineNumber >= 0) {
                  result.append("(").append(fileName).append(":").append(lineNumber).append(")");
              } else {
                  result.append("(").append(fileName).append(")");
              }
          } else {
              if (lineNumber >= 0) {
                  // The line number is actually the dex pc.
                  result.append("(Unknown Source:").append(lineNumber).append(")");
              } else {
                  result.append("(Unknown Source)");
              }
          }
          return result.toString();
          // END Android-changed: Fall back Unknown Source:<dex_pc> for unknown lineNumber.
      }
  
      /**
       * 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
       * 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;
  }
  