equlas()

[Shiva Mohan]

    
public class Chapter6 {
public static void main(String args[]){
obj1 oba=new obj1(1,2);
obj1 obb=new obj1(1,2) ;
if (oba.equals(obb)){  //-----------line1
System.out.println("oba == obb");}  
else {System.out.println("oba!=obb");}
obj2 ob2=new obj2();
if (ob2.equals(oba)) {//-----------------line2
System.out.println("ob2==oba");}   
else {System.out.println("ob2!=oba");
 
}
Boolean b1=new Boolean("true");
Boolean b2=new Boolean("yes");  
System.out.println(b2);
System.out.println (b1.equals(b2));  
}
 

}
 
class obj1{
private int x=0;
private int y=0;
obj1(int x,int y){
this.x=x;
this.y=y;
}
public int getX(){
return this.x;
}
public int getY(){
return this.y;
}
}
 
class obj2{
private int x=1;
private int y=2;
public boolean equals(Object ob){   
obj1 one=(obj1)ob;   //---------------------line3
if ((one.getX()==x)&&(one.getY()==y)){
return true;
}
else{
return false;
}
}
}

i got the lin1 execution.i have a doubt in line2.

1.ob2.equlas() means deep comparision.but here ob2 is obj2 object and having no value.and oba is obj1 objeact and having values (1,2).how come the result true is displaying.

2.How come the lin3 is not showing any classcastException

Thanks in advance.

[Meena R. Krishnan]

>>1.ob2.equlas() means deep comparision.but here ob2 is obj2 object and having no value.and oba is obj1 objeact and having values (1,2).how come the result true is displaying.

..is because, you are initializing it to 1 and 2 in the class declaration of obj2. Try changing the defaults to different values in obj2 and see what happens.


>>2.How come the lin3 is not showing any classcastException
Why? In the class obj2, as per your code, at line 3, it is expecting an object of type obj1 and in the main() you are passing obj1, therefore no exception.
At line 2, try passing ob2 instead

    
if (ob2.equals(ob2))

and you will see the exception.

[Keith Lynn]

In the obj2 class, you have two instance variables that are initialized when an object of type obj2 is created.

In this case you initialize them to 1 and 2.

These are the same values of the variables in the obj1 object you send.

The reason there isn't a ClassCastException is that you are converting the reference to type obj1, and you are send a reference of type obj1 to the equals method.