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;
 }
}