Analysis of argument passing in Java method

Rewrite the code considering the features of passing parameters by value and by reference. Describe what happens when variables z and a are passed to the method doIt(). What values will a, a.instanceNumber, a.x, a.y and z have after the method completes? What is the effect of the line a = new A(2); inside the method and why does it behave this way?

public class A {
    private static int y;
    private final int instanceNumber;
    private int x;

    public A(int instanceNumber) {
        this.instanceNumber = instanceNumber;
    }

    public String toString() {
        return String.valueOf(instanceNumber);
    }

    private static void doIt(int i, A a) {
        i = 11;
        a.x = 12;
        y = 13;
        a = new A(2); // ?
        a.x = 21;
        y = 22;
    }

    public static void main(String[] args) {
        A a = new A(1); // 1
        a.x = 1;
        y = 2;
        int z = 3;

        A.doIt(z, a);
    }
}