String constant pool??

[Joe San]

Guys,

Consider the code below from Dan Chisholm,

class MWC109 {
  public static void main(String args[]) {
    String a = "A", b = "B", c = a+b, d = a+b;
    System.out.print(((a+b)==(a+b)) + ","); //Line 1
    System.out.print((c==d) + ","); //Line 2
    System.out.print(c.equals(d));
}}

I was thinking that c = a+b; and d = a + b; will refer to the same onjects in the memory?

How come Line 1 prints false?? Anyone please?

[Vinayagar Karpagam]

If the declaration is modified like this,
final String a = "A", b = "B", c = a+b, d = a+b;
(c == d) will be true.

Hope you will be able to conclude.

[Joe San]

Vinayagar,

c == d will also return false.

[Muhammad Saifuddin]

Originally posted by Jothi Shankar Kumar Sankararaj:

c == d will also return false.

I don't understand why you got false on this condition(c==d)?

class MWC109 {
  public static void main(String args[]) {
   final String a = "A", b = "B", c = a+b, d = a+b;
    System.out.println(((a+b)==(a+b))); //Line 1
    System.out.println(c==d); //Line 2
    System.out.println(c.equals(d));
}
}

this programe prints "true" same in all 3 lines..

[Joe San]

I executed the code and it gave me false, false, true.

[Vinayagar Karpagam]

  final String a = "A";
        final String b = "B";
        String c = a + b;
        String d = a + b;
        System.out.println((a+b) == (a+b));
        System.out.println(c == d);

This program prints true and true.
When a or b or both changed to non-final, both are false.
Hope this helps.

[Mark Uppeteer]

true
true
true

regards,
Mark

[Anuragk kushwaha]

Hi Jothi..

yes you are write dear. the output is

false
false
true

As i know, String objects are immutable. yes it is 100% true.
then why concat operation performed on String.

in //line1

left side of == concat two string object(a and b)results into a 3rd new object lets say x,and right side of == also concat two string object(a and b)results into a fourth new object lets say y.
.........
then dear both x and y two different object created in memory....hence == operator returns false...

line 2 evaluated similer way...

hope this helps...Anu

[Muhammad Saifuddin]

Originally posted by anuragk kushwaha:

yes you are write dear. the output is

false
false
true

Originally posted by Jothi Shankar Kumar Sankararaj:
I executed the code and it gave me false, false, true.

hi Shankar & anuragk,

did you guys try my one.. which i wrote above.

[Joe San]

Saif,

I tried your code and it gave me true, true, true.

Can you tell me the logic why if one is a final String then it prints true?? Confused??

[Anuragk kushwaha]

Hi Saif,

yes, final makes a diffrenve, would you please discribe it.