Possible Duplicate:
difference between string object and string literal
When initializing a String object there are at least two ways, like such:
String s = "some string"; String s = new String("some string"); What's the difference?
- 3See this: difference between string object and string literalJon Lin– Jon Lin2011-11-08 11:11:23 +00:00Commented Nov 8, 2011 at 11:11
- 1Duplicate of : stackoverflow.com/q/3297867/977676COD3BOY– COD3BOY2011-11-08 11:18:27 +00:00Commented Nov 8, 2011 at 11:18
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4 Answers
The Java language has special handling for strings; a string literal automatically becomes a String object.
So in the first case, you're initializing the reference s to that String object.
In the second case, you're creating a new String object, passing in a reference to the original String object as a constructor parameter. In other words, you're creating a copy. The reference s is then initialized to refer to that copy.
answered Nov 8, 2011 at 11:11
Oliver Charlesworth
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Comments
In first case you can take this string from pool if it exist there. In second case you explicitly create new string object.
You can check this by these lines:
String s1 = "blahblah"; String s2 = "blahblah"; String s3 = new String("blahblah"); String s4 = s3.intern(); System.out.println(s1 == s2); System.out.println(s1 == s3); System.out.println(s2 == s3); System.out.println(s1 == s4); Output: true false false true 
3 Comments
Peter Lawrey
+1: You could add
String s4 = s3.intern(); System.out.println(s1 == s4);
mishadoff
Sure, it will complete our example
CaiNiaoCoder
thanks, you mentioned string pool. that's helpful, but I can only accept one as answer.
String s = "some string"; assigns that value to s from string pool (perm.gen.space) (creates one if it does not exist)
String s = new String("some string"); creates a new string with value given in constructor, memory allocated in heap
The first method is recommended as it will help to reuse the literal from string pool
Comments
Semantically, the first one assigns "some string" to s, while the second one assigns a copy of "some string" to s (since "some string" is already a String). I see no practical reasons to do this in 99.9% of cases, thus I would say that in most contexts, the only difference between the two lines is that:
- The second line is longer.
- The second line might consume more memory than the first one.
- As @Anish-Dasappan mentions, the second one will have it's value in heap, whereas the first one will be in the string pool - I'm not sure this has any interest for the programmer, but I might be missing a clever trick there.
