Java-Reference variable: super

class TestSuperFunc {
    public static void main(String[] args) {
        SubClass sub = new SubClass(10, 20, 30);
    }
}

class SuperClass {
    private int x = 0;
    private int y = 0;

    SuperClass() {}
    SuperClass(int value) {
        x = value;
        y = value;
    }
    SuperClass(int x, int y) {
        this.x = x;
        this.y = y;
    }
}

class SubClass extends SuperClass {
    private int z = 0;

    SubClass() {}
    SubClass(int value) {
        super(value);
        z = value;
    }
    SubClass(int x, int y, int z) {
        super(x, y);
        this.z = z;
    }
}