OO Programing in Java

Question

Hi Java People,
I have a class A:
class A {
public int a1;
public int a2;
public A() {
} // end A class
and a class B that extends A:
class B extends A {
public int B1;
public B() {
} // end B class
and somewhere in my code I have an instance aObj of class A and I want to create a instabce bObj of class B based on aObj but I don't want to explicitly copy the attributes something like:
B bObj = new B();
bObj.a1 = aObj.a1();
bObj.a2 = aObj.a2();
Can anyone help me?
I tried to make a B constructor:
public B(A aOgj) {
super = aObj; // this does't work, I new that super keyword is the instance object of the superclas
also I try in B constructor:
public B(A aOgj) {
this = (B) aObj; // it compiles succesfuly but nothing happens, this.a1 was diffrent then aObj.a1

Answer 1

public class A {
int x;
int y;
public A(){
public A(int x, int y){
setX(_x);
setY(_y);
public void setX(int _x){
this.x=_x;
public void setX(int _y){
this.y=_y;
public int getX(){ return x}
public int getY(){ return y};
public class B extends A{
//Ahora B tambien tiene los atributos x,y;
int z;
public B(){
super();
public B(int x, int y, int _z){
super(_x,_y);
this.z=_z;
public B (A a){
super(a.getX(),a.getY());
z=0;
}