using ThreadLocal()

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?

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(); } } }