1 class TLtest extends Thread { 2 main(String [] args)3 public static void main (String [] args) { 4 Data d = new Data (); 5 new ThreadTest (d, "A").start (); 6 new ThreadTest (d, "B").start (); 7 } 8 } 9 10 class Data { 11 12 private static ThreadLocal owner = new ThreadLocal () { 13 public Object initialValue () { return ("0"); } 14 }; 15 /* A thread will call `set' to set a value it wants an instance 16 of Data to associate with it and only it. */ set(String v)17 synchronized public void set (String v){owner.set (v);} 18 /* A thread will call `get' to get a value it wants an instance 19 of Data to associate with it and only it. */ get()20 synchronized public String get (){return (String)owner.get();} 21 } 22 23 class ThreadTest extends Thread { 24 25 public Data d; 26 ThreadTest(Data d, String name)27 ThreadTest (Data d, String name) { 28 super (name); 29 this.d = d; 30 } 31 run()32 public void run () { 33 34 int value = 0; 35 int ref = 0; 36 37 for (int i = 0; i < 20; i++) { 38 39 int rand = (int)(Math.random ()*20); 40 41 /* Read `value', ref is kept for comparison */ 42 value = Integer.parseInt (d.get()); 43 44 /* change `value' and ref by a random number, store `value'. */ 45 value += rand; ref += rand; 46 d.set (Integer.toString (value)); 47 48 try { 49 sleep((int)((Math.random() * 20))); 50 } catch (InterruptedException e) {} 51 } 52 53 /* If a thread didn't have private value to attach to the 54 instance of Data, results wouldn't be the same */ 55 if (ref == value) 56 System.out.println ("test OK."); 57 else 58 System.out.println ("test failed."); 59 } 60 } 61