Learning Java Lambdas

Example 2

The Example 2 class is another anonymous class but this time it closes over the server variable. It's an old style closure:

public class Example2 {
    // anonymous class (closure)
    void example() throws InterruptedException {
        Server server = new HttpServer();
        waitFor(new Condition() {
            @Override
            public Boolean isSatisfied() {
                return !server.isRunning();
            }
        });
    }
}

The bytecode is similar to the previous except that an instance of the Server class is newed up (at line 3.) and it's constructor called at line 5. The instance of the anonymous class $1 is still constructed with invokespecial (at line 11.) but this time it takes the instance of Server as an argument as well as the instance of the calling class.

To close over the server variable, it's ...