//: ThreadGroup1.java
//////////////////////////////////////////////////
// Copyright (c) Bruce Eckel, 1998
// Source code file from the book "Thinking in Java"
// All rights reserved EXCEPT as allowed by the
// following statements: You can freely use this file
// for your own work (personal or commercial),
// including modifications and distribution in
// executable form only. Permission is granted to use
// this file in classroom situations, including its
// use in presentation materials, as long as the book
// "Thinking in Java" is cited as the source.
// Except in classroom situations, you cannot copy
// and distribute this code; instead, the sole
// distribution point is http://www.BruceEckel.com
// (and official mirror sites) where it is
// freely available. You cannot remove this
// copyright and notice. You cannot distribute
// modified versions of the source code in this
// package. You cannot use this file in printed
// media without the express permission of the
// author. Bruce Eckel makes no representation about
// the suitability of this software for any purpose.
// It is provided "as is" without express or implied
// warranty of any kind, including any implied
// warranty of merchantability, fitness for a
// particular purpose or non-infringement. The entire
// risk as to the quality and performance of the
// software is with you. Bruce Eckel and the
// publisher shall not be liable for any damages
// suffered by you or any third party as a result of
// using or distributing software. In no event will
// Bruce Eckel or the publisher be liable for any
// lost revenue, profit, or data, or for direct,
// indirect, special, consequential, incidental, or
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// the theory of liability, arising out of the use of
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// and the publisher have been advised of the
// possibility of such damages. Should the software
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// address for non-code errors found in the book.)
/////////////////////////////////////////////////
// How thread groups control priorities
// of the threads inside them.
public class ThreadGroup1 {
public static void main(String[] args) {
// Get the system thread & print its Info:
ThreadGroup sys =
Thread.currentThread().getThreadGroup();
sys.list(); // (1)
// Reduce the system thread group priority:
sys.setMaxPriority(Thread.MAX_PRIORITY - 1);
// Increase the main thread priority:
Thread curr = Thread.currentThread();
curr.setPriority(curr.getPriority() + 1);
sys.list(); // (2)
// Attempt to set a new group to the max:
ThreadGroup g1 = new ThreadGroup("g1");
g1.setMaxPriority(Thread.MAX_PRIORITY);
// Attempt to set a new thread to the max:
Thread t = new Thread(g1, "A");
t.setPriority(Thread.MAX_PRIORITY);
g1.list(); // (3)
// Reduce g1's max priority, then attempt
// to increase it:
g1.setMaxPriority(Thread.MAX_PRIORITY - 2);
g1.setMaxPriority(Thread.MAX_PRIORITY);
g1.list(); // (4)
// Attempt to set a new thread to the max:
t = new Thread(g1, "B");
t.setPriority(Thread.MAX_PRIORITY);
g1.list(); // (5)
// Lower the max priority below the default
// thread priority:
g1.setMaxPriority(Thread.MIN_PRIORITY + 2);
// Look at a new thread's priority before
// and after changing it:
t = new Thread(g1, "C");
g1.list(); // (6)
t.setPriority(t.getPriority() -1);
g1.list(); // (7)
// Make g2 a child Threadgroup of g1 and
// try to increase its priority:
ThreadGroup g2 = new ThreadGroup(g1, "g2");
g2.list(); // (8)
g2.setMaxPriority(Thread.MAX_PRIORITY);
g2.list(); // (9)
// Add a bunch of new threads to g2:
for (int i = 0; i < 5; i++)
new Thread(g2, Integer.toString(i));
// Show information about all threadgroups
// and threads:
sys.list(); // (10)
System.out.println("Starting all threads:");
Thread[] all = new Thread[sys.activeCount()];
sys.enumerate(all);
for(int i = 0; i < all.length; i++)
if(!all[i].isAlive())
all[i].start();
// Suspends & Stops all threads in
// this group and its subgroups:
System.out.println("All threads started");
sys.suspend(); // Deprecated in Java 1.2
// Never gets here...
System.out.println("All threads suspended");
sys.stop(); // Deprecated in Java 1.2
System.out.println("All threads stopped");
}
} ///:~ |