/*
* Copyright © 2003 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*/
package java.lang;
/**
* A <i>thread</i> is a thread of execution in a program. The Java
* Virtual Machine allows an application to have multiple threads of
* execution running concurrently.
* <p>
* Every thread has a priority. Threads with higher priority are
* executed in preference to threads with lower priority.
* <p>
* There are two ways to create a new thread of execution. One is to
* declare a class to be a subclass of <code>Thread</code>. This
* subclass should override the <code>run</code> method of class
* <code>Thread</code>. An instance of the subclass can then be
* allocated and started. For example, a thread that computes primes
* larger than a stated value could be written as follows:
* <p><hr><blockquote><pre>
* class PrimeThread extends Thread {
* long minPrime;
* PrimeThread(long minPrime) {
* this.minPrime = minPrime;
* }
*
* public void run() {
* // compute primes larger than minPrime
* . . .
* }
* }
* </pre></blockquote><hr>
* <p>
* The following code would then create a thread and start it running:
* <p><blockquote><pre>
* PrimeThread p = new PrimeThread(143);
* p.start();
* </pre></blockquote>
* <p>
* The other way to create a thread is to declare a class that
* implements the <code>Runnable</code> interface. That class then
* implements the <code>run</code> method. An instance of the class can
* then be allocated, passed as an argument when creating
* <code>Thread</code>, and started. The same example in this other
* style looks like the following:
* <p><hr><blockquote><pre>
* class PrimeRun implements Runnable {
* long minPrime;
* PrimeRun(long minPrime) {
* this.minPrime = minPrime;
* }
*
* public void run() {
* // compute primes larger than minPrime
* . . .
* }
* }
* </pre></blockquote><hr>
* <p>
* The following code would then create a thread and start it running:
* <p><blockquote><pre>
* PrimeRun p = new PrimeRun(143);
* new Thread(p).start();
* </pre></blockquote>
* <p>
*
*
* @author unascribed
* @version 12/17/01 (CLDC 1.1)
* @see java.lang.Runnable
* @see java.lang.Runtime#exit(int)
* @see java.lang.Thread#run()
* @since JDK1.0, CLDC 1.0
*/
public
class Thread implements Runnable {
/* Thread priority */
private int priority = NORM_PRIORITY;
/* Internal thread queue */
private Thread threadQ;
/* What will be run. */
private Runnable target;
/* Thread name */
private char name[];
/**
* The minimum priority that a thread can have.
*/
public final static int MIN_PRIORITY = 1;
/**
* The default priority that is assigned to a thread.
*/
public final static int NORM_PRIORITY = 5;
/**
* The maximum priority that a thread can have.
*/
public final static int MAX_PRIORITY = 10;
/**
* Returns a reference to the currently executing
* <code>Thread</code> object.
*
* @return the currently executing thread.
*/
public static native Thread currentThread();
/* For autonumbering anonymous threads. */
private static int threadInitNumber;
private static synchronized int nextThreadNum() {
return ++threadInitNumber;
}
/**
* Causes the currently executing thread object
* to temporarily pause and allow other threads to execute.
*/
public static native void yield();
/**
* Causes the currently executing thread to sleep (temporarily cease
* execution) for the specified number of milliseconds. The thread
* does not lose ownership of any monitors.
*
* @param millis the length of time to sleep in milliseconds.
* @exception InterruptedException if another thread has interrupted
* the current thread. The <i>interrupted status</i> of the
* current thread is cleared when this exception is thrown.
* @see java.lang.Object#notify()
*/
public static native void sleep(long millis) throws InterruptedException;
/**
* Initialize a Thread.
*
* @param target the object whose run() method gets called
* @param name the name of the new thread
*/
private void init(Runnable target, String name) {
Thread parent = currentThread();
this.target = target;
this.name = name.toCharArray();
this.priority = parent.getPriority();
setPriority0(priority);
}
/**
* Allocates a new <code>Thread</code> object.
* <p>
* Threads created this way must have overridden their
* <code>run()</code> method to actually do anything.
*
* @see java.lang.Runnable
*/
public Thread() {
init(null, "Thread-" + nextThreadNum());
}
/**
* Allocates a new <code>Thread</code> object with the
* given name.
*
* Threads created this way must have overridden their
* <code>run()</code> method to actually do anything.
*
* @param name the name of the new thread.
*/
public Thread(String name) {
init(null, name);
}
/**
* Allocates a new <code>Thread</code> object with a
* specific target object whose <code>run</code> method
* is called.
*
* @param target the object whose <code>run</code> method is called.
*/
public Thread(Runnable target) {
init(target, "Thread-" + nextThreadNum());
}
/**
* Allocates a new <code>Thread</code> object with the given
* target and name.
*
* @param target the object whose <code>run</code> method is called.
* @param name the name of the new thread.
*/
public Thread(Runnable target, String name) {
init(target, name);
}
/**
* Causes this thread to begin execution; the Java Virtual Machine
* calls the <code>run</code> method of this thread.
* <p>
* The result is that two threads are running concurrently: the
* current thread (which returns from the call to the
* <code>start</code> method) and the other thread (which executes its
* <code>run</code> method).
*
* @exception IllegalThreadStateException if the thread was already
* started.
* @see java.lang.Thread#run()
*/
public synchronized native void start();
/**
* If this thread was constructed using a separate
* <code>Runnable</code> run object, then that
* <code>Runnable</code> object's <code>run</code> method is called;
* otherwise, this method does nothing and returns.
* <p>
* Subclasses of <code>Thread</code> should override this method.
*
* @see java.lang.Thread#start()
* @see java.lang.Runnable#run()
*/
public void run() {
if (target != null) {
target.run();
}
}
/**
* Interrupts this thread. In an implementation conforming
* to the CLDC Specification, this operation is not
* required to cancel or clean up any pending I/O operations
* that the thread may be waiting for.
*
* @since JDK 1.0, CLDC 1.1
*/
public void interrupt() {
interrupt0();
}
/**
* Tests if this thread is alive. A thread is alive if it has
* been started and has not yet died.
*
* @return <code>true</code> if this thread is alive;
* <code>false</code> otherwise.
*/
public final native boolean isAlive();
/**
* Changes the priority of this thread.
*
* @param newPriority priority to set this thread to
* @exception IllegalArgumentException If the priority is not in the
* range <code>MIN_PRIORITY</code> to
* <code>MAX_PRIORITY</code>.
* @see java.lang.Thread#getPriority()
* @see java.lang.Thread#MAX_PRIORITY
* @see java.lang.Thread#MIN_PRIORITY
*/
public final void setPriority(int newPriority) {
if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
throw new IllegalArgumentException();
}
setPriority0(priority = newPriority);
}
/**
* Returns this thread's priority.
*
* @return this thread's priority.
* @see java.lang.Thread#setPriority(int)
*/
public final int getPriority() {
return priority;
}
/**
* Returns this thread's name. Note that in CLDC the name
* of the thread can only be set when creating the thread.
*
* @return this thread's name.
*/
public final String getName() {
return String.valueOf(name);
}
/**
* Returns the current number of active threads in the virtual machine.
*
* @return the current number of active threads.
*/
public static native int activeCount();
/**
* Waits for this thread to die.
*
* @exception InterruptedException if another thread has interrupted
* the current thread. The <i>interrupted status</i> of the
* current thread is cleared when this exception is thrown.
*/
public synchronized final void join() throws InterruptedException {
while (isAlive()) {
wait(1000);
}
}
/**
* Returns a string representation of this thread, including the
* thread's name and priority.
*
* @return a string representation of this thread.
*/
public String toString() {
return "Thread[" + getName() + "," + getPriority() + "]";
}
/* Some private helper methods */
private native void setPriority0(int newPriority);
private native void interrupt0();
}
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