Java Tutorial/Thread/ThreadGroup
Содержание
Add thread to thread group
<source lang="java">
class ThreadGroupDemo1 {
public static void main(String[] args) {
ThreadGroup tg = new ThreadGroup("My ThreadGroup");
MyThread mt = new MyThread(tg, "My Thread");
mt.start();
}
} class MyThread extends Thread {
MyThread(ThreadGroup tg, String name) {
super(tg, name);
}
public void run() {
ThreadGroup tg = getThreadGroup();
System.out.println(tg.getName());
}
}</source>
Demonstrate thread groups.
<source lang="java">
class NewThread extends Thread {
boolean suspendFlag;
NewThread(String threadname, ThreadGroup tgOb) {
super(tgOb, threadname);
suspendFlag = false;
start();
}
public void run() {
try {
for (int i = 5; i > 0; i--) {
System.out.println(getName() + ": " + i);
Thread.sleep(1000);
synchronized (this) {
while (suspendFlag) {
wait();
}
}
}
} catch (Exception e) {
System.out.println("Exception in " + getName());
}
}
void mysuspend() {
suspendFlag = true;
}
synchronized void myresume() {
suspendFlag = false;
notify();
}
} class ThreadGroupDemo {
public static void main(String args[]) {
ThreadGroup groupA = new ThreadGroup("Group A");
ThreadGroup groupB = new ThreadGroup("Group B");
NewThread ob1 = new NewThread("One", groupA);
NewThread ob2 = new NewThread("Two", groupA);
NewThread ob3 = new NewThread("Three", groupB);
NewThread ob4 = new NewThread("Four", groupB);
groupA.list();
groupB.list();
Thread tga[] = new Thread[groupA.activeCount()];
groupA.enumerate(tga);
for (int i = 0; i < tga.length; i++) {
((NewThread) tga[i]).mysuspend();
}
try {
Thread.sleep(4000);
} catch (InterruptedException e) {
System.out.println("Main thread interrupted.");
}
System.out.println("Resuming Group A");
for (int i = 0; i < tga.length; i++) {
((NewThread) tga[i]).myresume();
}
try {
ob1.join();
ob2.join();
ob3.join();
ob4.join();
} catch (Exception e) {
System.out.println("Exception in Main thread");
}
}
}</source>
Get parent thread group
<source lang="java">
class Main {
public static void main(String[] args) throws Exception {
ThreadGroup tg = Thread.currentThread().getThreadGroup();
MyThread mt1 = new MyThread(tg, "first");
MyThread mt2 = new MyThread(tg, "second");
mt1.start();
mt2.start();
ThreadGroup parent = tg.getParent();
Thread[] list = new Thread[parent.activeCount()];
int count = parent.enumerate(list, true);
String[] thdinfo = new String[count];
for (int i = 0; i < count; i++)
thdinfo[i] = list[i].toString();
mt1.join();
mt2.join();
for (int i = 0; i < count; i++)
System.out.println(thdinfo[i]);
}
} class MyThread extends Thread {
MyThread(ThreadGroup tg, String name) {
super(tg, name);
}
public void run() {
for (char c = "A"; c <= "Z"; c++)
System.out.println(c);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
}
}</source>
Listing all threads and threadgroups in the VM
<source lang="java">
/*
* Copyright (c) 2004 David Flanagan. All rights reserved. * This code is from the book Java Examples in a Nutshell, 3nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose, * including teaching and use in open-source projects. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book, * please visit http://www.davidflanagan.ru/javaexamples3. */
import java.awt.BorderLayout; import java.io.PrintWriter; import java.io.StringWriter; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTextArea; /**
* 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 create a simple graphical user interface to display the
* threads in. This allows us to see the "event dispatch thread" used by AWT
* and Swing.
*/
public static void main(String[] args) {
// Create a simple Swing GUI
JFrame frame = new JFrame("ThreadLister Demo");
JTextArea textarea = new JTextArea();
frame.getContentPane().add(new JScrollPane(textarea), BorderLayout.CENTER);
frame.setSize(500, 400);
frame.setVisible(true);
// Get the threadlisting as a string using a StringWriter stream
StringWriter sout = new StringWriter(); // To capture the listing
PrintWriter out = new PrintWriter(sout);
ThreadLister.listAllThreads(out); // List threads to stream
out.close();
String threadListing = sout.toString(); // Get listing as a string
// Finally, display the thread listing in the GUI
textarea.setText(threadListing);
}
}</source>
