equals method

[Armel Moukoss]

Hi everybody,
Can anyone explains the result of this code :

public class Reference {
public static void main (String Args [] ){
Reference t1 = new Reference ();
Reference t2 = new Reference ();

if (t1.equals(t2)){
System.out.println ("Same content");
}else{
System.out.println ("Different content");
}
}
}
the output is : Different content. I thought it would be Same content.
Thank you

[Henry Wong]

the output is : Different content. I thought it would be Same content.

Well, since your "Reference" class doesn't override the equals() method, you are using the equals() method implementation from the Object class. The implementation of the equals() method of the Object class returns true only if the two objects are the exact same instance.

Henry

[Chandra Bhatt]

Hi Moukoss,

    
public class Reference {
public static void main (String Args [] ){
Reference t1 = new Reference ();
Reference t2 = new Reference ();
 
if (t1.equals(t2)){
System.out.println ("Same content");
}else{
System.out.println ("Different content");
}
}
}
 

If you dont override the equals() method that you have inherited from the Object class, you would get this result. Object class equals() method does nothing but returns true if references to the two objects are same. In your case you created two objects and references to both objects are different so they are different, and equals returns false.

Try this code if you want result true if you use equals to compare objects of class Reference:

    
public class Reference {
 
public boolean equals(Object o) {
    if(o.getClass() == this.getClass()) {
         return true;
    }
return false;
 
}
public static void main (String Args [] ){
Reference t1 = new Reference ();
Reference t2 = new Reference ();
 
if (t1.equals(t2)){
System.out.println ("Same content");
}else{
System.out.println ("Different content");
}
}
}

But you would often want to give your equals method a deeper meaning that what I have done.

Hope this helps you!
Thanks and Regards,
cmbhatt

[Scott Tiger]

i agree the upstairs .
check the j2se api:

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

[Armel Moukoss]

Thank you to everyone for your answer. I thought that the equals method was the same for Object, Integer,.. and so one. But i was wrong. thank you !!!