Question

public static void main(String args[]) throws Exception {
    int maxScore = 0;

Thread student = new Thread(client,????);
student.start();
}

I want student thread to change value of maxScore, how do I do it in Java? (Like in C we can pass the address of maxScore)

Answer 1

You can’t. There is no way you can change the value of a local variable from another thread.

You can, however, use a mutable type that has an int field, and pass it to the new thread. For example:

public class MutableInt {
    private int value;
    public void setValue(..) {..}
    public int getValue() {..};
}

(Apache commons-lang provide a MutableInt class which you can reuse)

Update: for a global variable you can simple use public static fields. Note that if you are willing not only to store some values in them, but also read them and do stuff depending on that, you would need to use synchronized blocks, or AtomicInteger, depending on the usages.