Initial revision

From-SVN: r102074
author: Tom Tromey <tromey@gcc.gnu.org> 2005-07-16 00:30:23 +0000
committer: Tom Tromey <tromey@gcc.gnu.org> 2005-07-16 00:30:23 +0000
commit: f911ba985aa7fe0096c386c5be385ac5825ea527 (patch)
tree: a0b991cf5866ae1d616639b906ac001811d74508 /libjava/classpath/java/lang/Throwable.java
parent: 6f4434b39b261de5317dc81ddfdd94d2e1d62b11 (diff)
download: gcc-f911ba985aa7fe0096c386c5be385ac5825ea527.zip
gcc-f911ba985aa7fe0096c386c5be385ac5825ea527.tar.gz
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diff --git a/libjava/classpath/java/lang/Throwable.java b/libjava/classpath/java/lang/Throwable.java
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+/* java.lang.Throwable -- Root class for all Exceptions and Errors
+   Copyright (C) 1998, 1999, 2002, 2004, 2005  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+package java.lang;
+
+import gnu.classpath.SystemProperties;
+
+import java.io.PrintStream;
+import java.io.PrintWriter;
+import java.io.Serializable;
+
+/**
+ * Throwable is the superclass of all exceptions that can be raised.
+ *
+ * <p>There are two special cases: {@link Error} and {@link RuntimeException}:
+ * these two classes (and their subclasses) are considered unchecked
+ * exceptions, and are either frequent enough or catastrophic enough that you
+ * do not need to declare them in <code>throws</code> clauses.  Everything
+ * else is a checked exception, and is ususally a subclass of
+ * {@link Exception}; these exceptions have to be handled or declared.
+ *
+ * <p>Instances of this class are usually created with knowledge of the
+ * execution context, so that you can get a stack trace of the problem spot
+ * in the code.  Also, since JDK 1.4, Throwables participate in "exception
+ * chaining."  This means that one exception can be caused by another, and
+ * preserve the information of the original.
+ *
+ * <p>One reason this is useful is to wrap exceptions to conform to an
+ * interface.  For example, it would be bad design to require all levels
+ * of a program interface to be aware of the low-level exceptions thrown
+ * at one level of abstraction. Another example is wrapping a checked
+ * exception in an unchecked one, to communicate that failure occured
+ * while still obeying the method throws clause of a superclass.
+ *
+ * <p>A cause is assigned in one of two ways; but can only be assigned once
+ * in the lifetime of the Throwable.  There are new constructors added to
+ * several classes in the exception hierarchy that directly initialize the
+ * cause, or you can use the <code>initCause</code> method. This second
+ * method is especially useful if the superclass has not been retrofitted
+ * with new constructors:<br>
+ * <pre>
+ * try
+ *   {
+ *     lowLevelOp();
+ *   }
+ * catch (LowLevelException lle)
+ *   {
+ *     throw (HighLevelException) new HighLevelException().initCause(lle);
+ *   }
+ * </pre>
+ * Notice the cast in the above example; without it, your method would need
+ * a throws clase that declared Throwable, defeating the purpose of chainig
+ * your exceptions.
+ *
+ * <p>By convention, exception classes have two constructors: one with no
+ * arguments, and one that takes a String for a detail message.  Further,
+ * classes which are likely to be used in an exception chain also provide
+ * a constructor that takes a Throwable, with or without a detail message
+ * string.
+ *
+ * <p>Another 1.4 feature is the StackTrace, a means of reflection that
+ * allows the program to inspect the context of the exception, and which is
+ * serialized, so that remote procedure calls can correctly pass exceptions.
+ *
+ * @author Brian Jones
+ * @author John Keiser
+ * @author Mark Wielaard
+ * @author Tom Tromey
+ * @author Eric Blake (ebb9@email.byu.edu)
+ * @since 1.0
+ * @status updated to 1.4
+ */
+public class Throwable implements Serializable
+{
+  /**
+   * Compatible with JDK 1.0+.
+   */
+  private static final long serialVersionUID = -3042686055658047285L;
+
+  /**
+   * The detail message.
+   *
+   * @serial specific details about the exception, may be null
+   */
+  private final String detailMessage;
+
+  /**
+   * The cause of the throwable, including null for an unknown or non-chained
+   * cause. This may only be set once; so the field is set to
+   * <code>this</code> until initialized.
+   *
+   * @serial the cause, or null if unknown, or this if not yet set
+   * @since 1.4
+   */
+  private Throwable cause = this;
+
+  /**
+   * The stack trace, in a serialized form.
+   *
+   * @serial the elements of the stack trace; this is non-null, and has
+   *         no null entries
+   * @since 1.4
+   */
+  private StackTraceElement[] stackTrace;
+
+  /**
+   * Instantiate this Throwable with an empty message. The cause remains
+   * uninitialized.  {@link #fillInStackTrace()} will be called to set
+   * up the stack trace.
+   */
+  public Throwable()
+  {
+    this((String) null);
+  }
+
+  /**
+   * Instantiate this Throwable with the given message. The cause remains
+   * uninitialized.  {@link #fillInStackTrace()} will be called to set
+   * up the stack trace.
+   *
+   * @param message the message to associate with the Throwable
+   */
+  public Throwable(String message)
+  {
+    fillInStackTrace();
+    detailMessage = message;
+  }
+
+  /**
+   * Instantiate this Throwable with the given message and cause. Note that
+   * the message is unrelated to the message of the cause.
+   * {@link #fillInStackTrace()} will be called to set up the stack trace.
+   *
+   * @param message the message to associate with the Throwable
+   * @param cause the cause, may be null
+   * @since 1.4
+   */
+  public Throwable(String message, Throwable cause)
+  {
+    this(message);
+    this.cause = cause;
+  }
+
+  /**
+   * Instantiate this Throwable with the given cause. The message is then
+   * built as <code>cause == null ? null : cause.toString()</code>.
+   * {@link #fillInStackTrace()} will be called to set up the stack trace.
+   *
+   * @param cause the cause, may be null
+   * @since 1.4
+   */
+  public Throwable(Throwable cause)
+  {
+    this(cause == null ? null : cause.toString(), cause);
+  }
+
+  /**
+   * Get the message associated with this Throwable.
+   *
+   * @return the error message associated with this Throwable, may be null
+   */
+  public String getMessage()
+  {
+    return detailMessage;
+  }
+
+  /**
+   * Get a localized version of this Throwable's error message.
+   * This method must be overridden in a subclass of Throwable
+   * to actually produce locale-specific methods.  The Throwable
+   * implementation just returns getMessage().
+   *
+   * @return a localized version of this error message
+   * @see #getMessage()
+   * @since 1.1
+   */
+  public String getLocalizedMessage()
+  {
+    return getMessage();
+  }
+
+  /**
+   * Returns the cause of this exception, or null if the cause is not known
+   * or non-existant. This cause is initialized by the new constructors,
+   * or by calling initCause.
+   *
+   * @return the cause of this Throwable
+   * @since 1.4
+   */
+  public Throwable getCause()
+  {
+    return cause == this ? null : cause;
+  }
+
+  /**
+   * Initialize the cause of this Throwable.  This may only be called once
+   * during the object lifetime, including implicitly by chaining
+   * constructors.
+   *
+   * @param cause the cause of this Throwable, may be null
+   * @return this
+   * @throws IllegalArgumentException if cause is this (a Throwable can't be
+   *         its own cause!)
+   * @throws IllegalStateException if the cause has already been set
+   * @since 1.4
+   */
+  public Throwable initCause(Throwable cause)
+  {
+    if (cause == this)
+      throw new IllegalArgumentException();
+    if (this.cause != this)
+      throw new IllegalStateException();
+    this.cause = cause;
+    return this;
+  }
+
+  /**
+   * Get a human-readable representation of this Throwable. The detail message
+   * is retrieved by getLocalizedMessage().  Then, with a null detail
+   * message, this string is simply the object's class name; otherwise
+   * the string is <code>getClass().getName() + ": " + message</code>.
+   *
+   * @return a human-readable String represting this Throwable
+   */
+  public String toString()
+  {
+    String msg = getLocalizedMessage();
+    return getClass().getName() + (msg == null ? "" : ": " + msg);
+  }
+
+  /**
+   * Print a stack trace to the standard error stream. This stream is the
+   * current contents of <code>System.err</code>. The first line of output
+   * is the result of {@link #toString()}, and the remaining lines represent
+   * the data created by {@link #fillInStackTrace()}. While the format is
+   * unspecified, this implementation uses the suggested format, demonstrated
+   * by this example:<br>
+   * <pre>
+   * public class Junk
+   * {
+   *   public static void main(String args[])
+   *   {
+   *     try
+   *       {
+   *         a();
+   *       }
+   *     catch(HighLevelException e)
+   *       {
+   *         e.printStackTrace();
+   *       }
+   *   }
+   *   static void a() throws HighLevelException
+   *   {
+   *     try
+   *       {
+   *         b();
+   *       }
+   *     catch(MidLevelException e)
+   *       {
+   *         throw new HighLevelException(e);
+   *       }
+   *   }
+   *   static void b() throws MidLevelException
+   *   {
+   *     c();
+   *   }
+   *   static void c() throws MidLevelException
+   *   {
+   *     try
+   *       {
+   *         d();
+   *       }
+   *     catch(LowLevelException e)
+   *       {
+   *         throw new MidLevelException(e);
+   *       }
+   *   }
+   *   static void d() throws LowLevelException
+   *   {
+   *     e();
+   *   }
+   *   static void e() throws LowLevelException
+   *   {
+   *     throw new LowLevelException();
+   *   }
+   * }
+   * class HighLevelException extends Exception
+   * {
+   *   HighLevelException(Throwable cause) { super(cause); }
+   * }
+   * class MidLevelException extends Exception
+   * {
+   *   MidLevelException(Throwable cause)  { super(cause); }
+   * }
+   * class LowLevelException extends Exception
+   * {
+   * }
+   * </pre>
+   * <p>
+   * <pre>
+   *  HighLevelException: MidLevelException: LowLevelException
+   *          at Junk.a(Junk.java:13)
+   *          at Junk.main(Junk.java:4)
+   *  Caused by: MidLevelException: LowLevelException
+   *          at Junk.c(Junk.java:23)
+   *          at Junk.b(Junk.java:17)
+   *          at Junk.a(Junk.java:11)
+   *          ... 1 more
+   *  Caused by: LowLevelException
+   *          at Junk.e(Junk.java:30)
+   *          at Junk.d(Junk.java:27)
+   *          at Junk.c(Junk.java:21)
+   *          ... 3 more
+   * </pre>
+   */
+  public void printStackTrace()
+  {
+    printStackTrace(System.err);
+  }
+
+  /**
+   * Print a stack trace to the specified PrintStream. See
+   * {@link #printStackTrace()} for the sample format.
+   *
+   * @param s the PrintStream to write the trace to
+   */
+  public void printStackTrace(PrintStream s)
+  {
+    s.print(stackTraceString());
+  }
+
+  /**
+   * Prints the exception, the detailed message and the stack trace
+   * associated with this Throwable to the given <code>PrintWriter</code>.
+   * The actual output written is implemention specific. Use the result of
+   * <code>getStackTrace()</code> when more precise information is needed.
+   *
+   * <p>This implementation first prints a line with the result of this
+   * object's <code>toString()</code> method.
+   * <br>
+   * Then for all elements given by <code>getStackTrace</code> it prints
+   * a line containing three spaces, the string "at " and the result of calling
+   * the <code>toString()</code> method on the <code>StackTraceElement</code>
+   * object. If <code>getStackTrace()</code> returns an empty array it prints
+   * a line containing three spaces and the string
+   * "&lt;&lt;No stacktrace available&gt;&gt;".
+   * <br>
+   * Then if <code>getCause()</code> doesn't return null it adds a line
+   * starting with "Caused by: " and the result of calling
+   * <code>toString()</code> on the cause.
+   * <br>
+   * Then for every cause (of a cause, etc) the stacktrace is printed the
+   * same as for the top level <code>Throwable</code> except that as soon
+   * as all the remaining stack frames of the cause are the same as the
+   * the last stack frames of the throwable that the cause is wrapped in
+   * then a line starting with three spaces and the string "... X more" is
+   * printed, where X is the number of remaining stackframes.
+   *
+   * @param pw the PrintWriter to write the trace to
+   * @since 1.1
+   */
+  public void printStackTrace (PrintWriter pw)
+  {
+    pw.print(stackTraceString());
+  }
+
+  /*
+   * We use inner class to avoid a static initializer in this basic class.
+   */
+  private static class StaticData
+  {
+    static final String nl = SystemProperties.getProperty("line.separator");
+  }
+
+  // Create whole stack trace in a stringbuffer so we don't have to print
+  // it line by line. This prevents printing multiple stack traces from
+  // different threads to get mixed up when written to the same PrintWriter.
+  private String stackTraceString()
+  {
+    StringBuffer sb = new StringBuffer();
+
+    // Main stacktrace
+    StackTraceElement[] stack = getStackTrace();
+    stackTraceStringBuffer(sb, this.toString(), stack, 0);
+
+    // The cause(s)
+    Throwable cause = getCause();
+    while (cause != null)
+      {
+	// Cause start first line
+        sb.append("Caused by: ");
+
+        // Cause stacktrace
+        StackTraceElement[] parentStack = stack;
+        stack = cause.getStackTrace();
+	if (parentStack == null || parentStack.length == 0)
+	  stackTraceStringBuffer(sb, cause.toString(), stack, 0);
+	else
+	  {
+	    int equal = 0; // Count how many of the last stack frames are equal
+	    int frame = stack.length-1;
+	    int parentFrame = parentStack.length-1;
+	    while (frame > 0 && parentFrame > 0)
+	      {
+		if (stack[frame].equals(parentStack[parentFrame]))
+		  {
+		    equal++;
+		    frame--;
+		    parentFrame--;
+		  }
+		else
+		  break;
+	      }
+	    stackTraceStringBuffer(sb, cause.toString(), stack, equal);
+	  }
+        cause = cause.getCause();
+      }
+
+    return sb.toString();
+  }
+
+  // Adds to the given StringBuffer a line containing the name and
+  // all stacktrace elements minus the last equal ones.
+  private static void stackTraceStringBuffer(StringBuffer sb, String name,
+					StackTraceElement[] stack, int equal)
+  {
+    String nl = StaticData.nl;
+    // (finish) first line
+    sb.append(name);
+    sb.append(nl);
+
+    // The stacktrace
+    if (stack == null || stack.length == 0)
+      {
+	sb.append("   <<No stacktrace available>>");
+	sb.append(nl);
+      }
+    else
+      {
+	for (int i = 0; i < stack.length-equal; i++)
+	  {
+	    sb.append("   at ");
+	    sb.append(stack[i] == null ? "<<Unknown>>" : stack[i].toString());
+	    sb.append(nl);
+	  }
+	if (equal > 0)
+	  {
+	    sb.append("   ...");
+	    sb.append(equal);
+	    sb.append(" more");
+	    sb.append(nl);
+	  }
+      }
+  }
+
+  /**
+   * Fill in the stack trace with the current execution stack.
+   *
+   * @return this same throwable
+   * @see #printStackTrace()
+   */
+  public Throwable fillInStackTrace()
+  {
+    vmState = VMThrowable.fillInStackTrace(this);
+    stackTrace = null; // Should be regenerated when used.
+
+    return this;
+  }
+
+  /**
+   * Provides access to the information printed in {@link #printStackTrace()}.
+   * The array is non-null, with no null entries, although the virtual
+   * machine is allowed to skip stack frames.  If the array is not 0-length,
+   * then slot 0 holds the information on the stack frame where the Throwable
+   * was created (or at least where <code>fillInStackTrace()</code> was
+   * called).
+   *
+   * @return an array of stack trace information, as available from the VM
+   * @since 1.4
+   */
+  public StackTraceElement[] getStackTrace()
+  {
+    if (stackTrace == null)
+      if (vmState == null)
+	stackTrace = new StackTraceElement[0];
+      else 
+	{
+	  stackTrace = vmState.getStackTrace(this);
+	  vmState = null; // No longer needed
+	}
+
+    return stackTrace;
+  }
+
+  /**
+   * Change the stack trace manually. This method is designed for remote
+   * procedure calls, which intend to alter the stack trace before or after
+   * serialization according to the context of the remote call.
+   * <p>
+   * The contents of the given stacktrace is copied so changes to the
+   * original array do not change the stack trace elements of this
+   * throwable.
+   *
+   * @param stackTrace the new trace to use
+   * @throws NullPointerException if stackTrace is null or has null elements
+   * @since 1.4
+   */
+  public void setStackTrace(StackTraceElement[] stackTrace)
+  {
+    int i = stackTrace.length;
+    StackTraceElement[] st = new StackTraceElement[i];
+
+    while (--i >= 0)
+      {
+	st[i] = stackTrace[i];
+	if (st[i] == null)
+	  throw new NullPointerException("Element " + i + " null");
+      }
+
+    this.stackTrace = st;
+  }
+
+  /**
+   * VM state when fillInStackTrace was called.
+   * Used by getStackTrace() to get an array of StackTraceElements.
+   * Cleared when no longer needed.
+   */
+  private transient VMThrowable vmState;
+}
author	Tom Tromey <tromey@gcc.gnu.org>	2005-07-16 00:30:23 +0000
committer	Tom Tromey <tromey@gcc.gnu.org>	2005-07-16 00:30:23 +0000
commit	f911ba985aa7fe0096c386c5be385ac5825ea527 (patch)
tree	a0b991cf5866ae1d616639b906ac001811d74508 /libjava/classpath/java/lang/Throwable.java
parent	6f4434b39b261de5317dc81ddfdd94d2e1d62b11 (diff)
download	gcc-f911ba985aa7fe0096c386c5be385ac5825ea527.zip gcc-f911ba985aa7fe0096c386c5be385ac5825ea527.tar.gz gcc-f911ba985aa7fe0096c386c5be385ac5825ea527.tar.bz2