Need help to understand the diff bet "==" vs "equals()" method

[Karthik Balasubramanian]

1.String s1="abc"+"def";
2.String s2=new String (s1);
3.if (s1==s2)
4. System.out.println("== succeeded");
5.if (s1.equals(s2))
6. System.out.println(".equals() succeeded");
For the above question...the answer is
Line 6 executes and Line 4 does not.
I do not understand where I can use "==" operator...where I should use "equals()" method?
Please help me out by saying how this works?
Thanks
Karthik

[Manish Hatwalne]

== checks whether two referrences are referring to the *same object* on the heap, whereas the equals method (if implemented correctly) checks if the contents of two objects are *logically equal* or not.
See if this example helps -
Integer a = new Integer(7);
Integer b = new Integer(7);
Integer x = new Integer(1);
Integer y = x;
Here -
a == b --> returns false;
a.equals(b) --> returns true;
AND
x == y --> returns true;
x.equals(y) --> returns true;
HTH,
- Manish

[Karthik Balasubramanian]

Thanks Manish. Now I have a clear understanding.
Thanks
Karthik