java - Multithreading: Switching context -

i have written small sample code:

public class button2 implements runnable{         jbutton jbutton = new jbutton();     static boolean changecontext = false;         public button2(){         jbutton.settext("buttontwo");         jbutton.addactionlistener(new actionlistener() {             @override             public void actionperformed(actionevent e) {                 changecontext = true;                 ((jbutton)e.getsource()).setenabled(false);             }         });     }     @override     public void run() {         system.out.println("buttontwo run...");         jbutton.setenabled(true);         while(true){             if(changecontext)                 break;         }         changecontext = false;             } } 

when run like:

button2 threadtwo = new button2(); thread thread2;             try{                 thread2 = new thread(threadtwo);             thread2.start();             thread2.join();             }catch(exception ex){                 system.out.println("Ëxception caught");             } 

it never comes out, after clicking button.

if add sysout or thread.sleep(1) after while(true) in run method, comes out of while loop. can possible reason?

i assume you're running bottom portion on edt. you're creating button (and add ui somehow) start thread , make edt wait thread die (thread2.join()), hence edt can't process events , changecontext = true never called.

that adding makes loop end due missing braces:

this ends loop if changecontext true:

if(changecontext)    break; 

i assume did this:

if(changecontext)    thread.sleep(1);    break; 

the above calls sleep if changecontext true , ends loop (the break not inside if-block anymore. if want consistent behavior write this:

if(changecontext) {    thread.sleep(1);    break; } 

btw, apple had security issue last year had similar source (a double break , no braces).