threadlister.java

《Java 3D编程》的源代码

// This example is from _Java Examples in a Nutshell_. (http://www.oreilly.com)
// Copyright (c) 1997 by David Flanagan
// This example is provided WITHOUT ANY WARRANTY either expressed or implied.
// You may study, use, modify, and distribute it for non-commercial purposes.
// For any commercial use, see http://www.davidflanagan.com/javaexamples

package org.selman.java3d.book.common;

import java.io.*;

/**
 * This class contains a useful static method for listing all threads
 * and threadgroups in the VM.  It also has a simple main() method so it
 * can be run as a standalone program.
 **/
public class ThreadLister {
	/** Display information about a thread. */
	private static void printThreadInfo( PrintWriter out, Thread t, 
		String indent )
	{
		if (t == null) return;
		out.println( indent + "Thread: " + t.getName( ) +
			"  Priority: " + t.getPriority( ) +
			(t.isDaemon( )?" Daemon":"") +
			(t.isAlive( )?"":" Not Alive"));
	}

	/** Display info about a thread group and its threads and groups */
	private static void printGroupInfo( PrintWriter out, ThreadGroup g, 
		String indent )
	{
		if (g == null) return;
		int num_threads = g.activeCount( );
		int num_groups = g.activeGroupCount( );
		Thread[] threads = new Thread[num_threads];
		ThreadGroup[] groups = new ThreadGroup[num_groups];

		g.enumerate( threads, false );
		g.enumerate( groups, false );

		out.println( indent + "Thread Group: " + g.getName( ) + 
			"  Max Priority: " + g.getMaxPriority( ) +
			(g.isDaemon( )?" Daemon":""));

		for(int i = 0; i < num_threads; i++)
			printThreadInfo( out, threads[i], indent + "    " );
		for(int i = 0; i < num_groups; i++)
			printGroupInfo( out, groups[i], indent + "    " );
	}

	/** Find the root thread group and list it recursively */
	public static void listAllThreads( PrintWriter out )
	{
		ThreadGroup current_thread_group;
		ThreadGroup root_thread_group;
		ThreadGroup parent;

		// Get the current thread group
		current_thread_group = Thread.currentThread( ).getThreadGroup( );

		// Now go find the root thread group
		root_thread_group = current_thread_group;
		parent = root_thread_group.getParent( );
		while(parent != null)
		{
			root_thread_group = parent;
			parent = parent.getParent( );
		}

		// And list it, recursively
		printGroupInfo( out, root_thread_group, "" );
	}

	/**
	* The main() method:  just print the list of threads to the console
	**/
	public static void main( String[] args )
	{
		PrintWriter out = new PrintWriter( new OutputStreamWriter( System.out ) );
		ThreadLister.listAllThreads( out );
		out.flush( );
	}

	/**
	* This nested class is a simple applet that displays the output of
	* ThreadLister.listAllThreads() when run from an the start() method of
	* an applet.  The output from an applet is typically different than the
	* output when run from a standalone program.
	**/
	public static class Applet extends java.applet.Applet
	{
		java.awt.TextArea textarea;  // Where to display the output.

		/** Create a text area to put our listing in */
		public void init( )
		{
			textarea = new java.awt.TextArea( );
			this.setLayout( new java.awt.BorderLayout( ) );
			this.add( "Center", textarea );
		}

		/** When the applet starts, list all the threads */
		public void start( )
		{
			StringWriter sout = new StringWriter( );  // Capture listing in a string
			PrintWriter out = new PrintWriter( sout );
			ThreadLister.listAllThreads( out );
			out.flush( );
			textarea.setText( sout.toString( ) );       // Display the listing
		}
	}
}