What's the difference between String s = "something"; and String s = new String("something");

Question

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?

Answer 1

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.

Answer 2

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

Answer 3

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

Answer 4

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:

1. The second line is longer.
2. The second line might consume more memory than the first one.
3. 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.