Setting outer variable from anonymous inner class

Question

Is there any way to access caller-scoped variables from an anonymous inner class in Java?

Here\'s the sample code to understand what I need:

public L         


        

Answer 1

You need a 'container' to hold your value. You, however, do not have to create a container class. You may use classes in the java.util.concurrent.atomic package. They provide an immutable wrapper for a value along with a set and a get method. You have AtomicInteger, AtomicBoolean, AtomicReference (for your objects) e.t.c

In the outer method:

final AtomicLong resultHolder = new AtomicLong();

In the anonymous inner class method

long result = getMyLongValue();
resultHolder.set(result);

Later in your outer method

return resultHolder.get();

Here's an example.

public Long getNumber() {
   final AtomicLong resultHolder = new AtomicLong();
   Session session = new Session();
   session.doWork(new Work() {
       public void execute() {
           //Inside anonymous inner class
           long result = getMyLongValue();
           resultHolder.set(result);
       }
   });
   return resultHolder.get(); //Returns the value of result
}