Why does 'concat' not change String?

Question

String s1 = "Sk";
s1.concat(" Y");
System.out.println("s1 refers to "+s1);

The above code generates the output "Sk" and not "Sk Y". I hope I'm explaining clear enough.Why is this ?

concat does not change the string, java strings are immutable. try s1 = s1.concat(" Y"). — pete23, Jun 28 '15 at 09:09

score 3 · Accepted Answer · answered Jun 28 '15 at 09:09

3

s1.concat(" Y"); doesn't alter s1 (it can't, since Strings are immutable).

It returns a new String :

String s2 = s1.concat(" Y");
System.out.println("s2 refers to "+s2);

answered Jun 28 '15 at 09:09

Eran

Can You explain immutable in more details or specify a link ? – dumbPotato21 Jun 28 '15 at 09:58
@Shashwat There's not much to explain. Immutable object means you can't change its state after you create it. When you write `String s1 = "Sk";`, `s1` refers to an immutable object, so any method you call on `s1` won't change the content of that String. On the other hand, StringBuilder is a mutable object. calling the `append` method of a StringBuilder object changes the content of that object. – Eran Jun 28 '15 at 10:04
http://stackoverflow.com/questions/279507/what-is-meant-by-immutable – Stephen C Jun 28 '15 at 11:03

1 Answers1