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  Tutorial: ThreadLocal Variables for Storing Thread-Specific State Information

ThreadLocal Variables for Storing Thread-Specific State Information MULTITHREADING IN SWING The Swing component set was first introduced in 1996, to be used in conjunction with the 1.1 version of what was then known as the Java Development Kit (JDK).

Tutorial Details:

THREADLOCAL VARIABLES FOR STORING THREAD-SPECIFIC STATE INFORMATION

Have you ever needed variables that were local to the scope of a thread, where each thread managed its storage, and it would be impossible for one thread to access the state information of another thread? The standard libraries offer two classes that provide this capability: ThreadLocal and InheritableThreadLocal.

Let\'s look at a simple use of the classes.

import java.util.Random;

public class ThreadLocal1 {

// Define/create thread local variable
static ThreadLocal threadLocal =
new ThreadLocal();
// Create class variable
static volatile int counter = 0;
// For random number generation
static Random random = new Random();

// Displays thread local variable, counter,
// and thread name
private static void displayValues() {
System.out.println (
threadLocal.get() + \"\\t\" + counter +
\"\\t\" + Thread.currentThread().getName());
}

public static void main (String args[]) {

// Each thread increments counter
// Displays variable info
// And sleeps for the random amount of time
// Before displaying info again
Runnable runner = new Runnable() {
public void run() {
synchronized(ThreadLocal1.class) {
counter++;
}
threadLocal.set(
new Integer(random.nextInt(1000)));
displayValues();
try {
Thread.sleep (
((Integer)threadLocal.get()).intValue());
displayValues();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};

// Increment counter, access thread local from
// a different thread, and display the values
synchronized(ThreadLocal1.class) {
counter++;
}
threadLocal.set(
new Integer(random.nextInt(1000)));
displayValues();

// Here\'s where the other threads
// are actually created
for (int i=0; i<5; i++) {
Thread t = new Thread(runner);
t.start();
}
}
}







 

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