Equal return False. What's wrong with this code?

Question

I have java syntax. Sory I'm still not figure out why this happen.

public class TestString {
  public static void main(String [] args){
    int i=-1;
    String a=((Object)i).toString();
    if(a=="-1"){
        System.out.println("Same");
    }else{
        System.out.println("Not");
    }
  }
}

And then the result is "Not" what the problems why -1 string different with -1 int in object?

try to print a and see the difference ;) – Tugrul Sep 06 '13 at 08:38 — Tugrul, Sep 06 '13 at 08:38
Use .equals() to compare the string – Rakesh KR Sep 06 '13 at 08:39 — Rakesh KR, Sep 06 '13 at 08:39

Suresh Atta · Answer 1 · 2013-09-06T08:43:19.497

5

You have to use .equals() on string to compare.

String's equal method overridden in such a way.

Try

public class TestString {
  public static void main(String [] args){
    int i=-1;
    String a=((Object)i).toString();
    if(a.equals("-1")){
        System.out.println("Same");
    }else{
        System.out.println("Not");
    }
  }
}

edited Sep 06 '13 at 08:43

answered Sep 06 '13 at 08:37

Suresh Atta

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score 0 · Answer 2 · answered Sep 06 '13 at 08:37

0

Strings have to be compared with the .equals() method.

answered Sep 06 '13 at 08:37

tom

2,735
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Thanks sory I come from C# behavior.. thanks – mrhands Sep 06 '13 at 08:38

score 0 · Answer 3 · answered Sep 06 '13 at 08:39

You are using reference equality instead of object equality.

Since "-1" in the literal table has a different heap address than a newly allocated a, it returns false.

If for some reason you find yourself allocating a lot of String objects that share the same value(s) and want to test them by reference instead, consider using String#intern():

final String a = [...].intern(); // allocated
if (a == SOME_INTERNED_STRING_1) {
  [...]
else if (a == SOME_INTERNED_STRING_2) {
  [...]
}

score 0 · Answer 4 · answered Sep 06 '13 at 08:41

0

==

compares reference which is not same in your case so if you want to compare string values then use

.equals() method

answered Sep 06 '13 at 08:41

ankit

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score 0 · Answer 5 · answered Sep 06 '13 at 08:44

0

The == operator checks to see if two objects are exactly the same object . You can go for equals method to check if the value are equal or not

answered Sep 06 '13 at 08:44

SpringLearner

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The objects are not even accessed when using `==` (reference equals) operator. The only thing being tested is their heap addresses. – Tadas S Sep 06 '13 at 08:45

Equal return False. What's wrong with this code?

5 Answers5