Returning value from Thread

Question

I have a method with a HandlerThread. A value gets changed inside the Thread and I'd like to return it to the test() method. Is there a way to do this?

public void test() {        Thread uiThread = new HandlerThread("UIHandler"){         public synchronized void run(){             int value;              value = 2; //To be returned to test()         }     };     uiThread.start(); } 

Answer 1

Usually you would do it something like this

 public class Foo implements Runnable {      private volatile int value;       @Override      public void run() {         value = 2;      }       public int getValue() {          return value;      }  } 

Then you can create the thread and retrieve the value (given that the value has been set)

Foo foo = new Foo(); Thread thread = new Thread(foo); thread.start(); thread.join(); int value = foo.getValue(); 

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tl;dr a thread cannot return a value (at least not without a callback mechanism). You should reference a thread like an ordinary class and ask for the value.