Question

public class test {

    public static void main(String[] args) throws Exception {

        final int num = 111;

        new Thread() {
            @Override
            public void run() {
                num = 222;
            }
        }.start();

    }
}

I want to change the value of num however I can only do that if I set it to final which would not let me modify this. In other languages such as C we can use pointers but Java cannot?

Answer 1

Java has neither closure nor pointers.

A solution would be to make the num static in the class :

public class test {
    static int num = 111;
    public static void main(String[] args) throws Exception {
        new Thread() {
            @Override
            public void run() {
                num = 222;
            }
        }.start();
    }
}

Another solution would be to use an object like AtomicInteger. You can’t change the value of the variable but you can change the content of the value :

public class test {
    public static void main(String[] args) throws Exception {
        final AtomicInteger num = new AtomicInteger(111);
        new Thread() {
            @Override
            public void run() {
                num.set(222);
            }
        }.start();
    }
}