when to go for new string instead of string literal in java

Question

I know when we use String s = new String("abc"); JVM will create the object in heap and when we use String s = "abc"; the object gets created in String constant pool.

IMO, using String s = "abc"; serves our purpose. In which case we have to go for new String("abc");

When you don't want string to be cached OR it's a very long string — Azodious, Jul 07 '16 at 14:00
@Azodious but you're still creating the string literal in either case. — Andy Turner, Jul 07 '16 at 14:00
Is this an opinion or a question? Because if it's a question, there is MORE than enough information on how and why objects (not just strings) are created the way they are. — durbnpoisn, Jul 07 '16 at 14:00
@AndyTurner but that won't be cached in pool. that's just syntax. — Azodious, Jul 07 '16 at 14:01
@AndyTurner well, that's what `intern` is for. so yes, i'm confident about this. — Azodious, Jul 07 '16 at 14:03
@Azodious no, intern is for if you're loading a string from some external data source and want it to be in the string pool. If you've got `new String("foo")` in your source code, you've got `"foo"` in your string pool. — Andy Turner, Jul 07 '16 at 14:04
@AndyTurner so `new String("foo")` will create two objects? on heap and string pool. is that correct? — Azodious, Jul 07 '16 at 14:06
@Azodious correct. Well actually, executing `new String("foo")` doesn't create two objects, it just creates one - the `"foo"` already existed. But yes, two objects with the value `"foo"` exist after that is executed for the first time. — Andy Turner, Jul 07 '16 at 14:06
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/116702/discussion-between-azodious-and-andy-turner). — Azodious, Jul 07 '16 at 14:09

score 2 · Accepted Answer · answered Jul 07 '16 at 14:01

2

It is never necessary to create a new String object from a string literal - in fact, it is unnecessarily inefficient.

String objects are immutable, so you never have to make a defensive copy of a String object.

answered Jul 07 '16 at 14:01

Jesper

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I can think of a few odd corner cases where you do want different instances of the same string... – assylias Jul 07 '16 at 14:07
@assylias please expand :) – Andy Turner Jul 07 '16 at 14:08
@AndyTurner say you send a query to a rest WS and the query params need to be stored in a map because a badly written API forces you to, and you want to send a list (server/ws?abc=1&abc=2&abc=3), you can build an IdentityHashMap and `map.put(new String("abc"), 1); map.put(new String("abc"), 2); etc.`. I insist on the "odd" bit of my initial comment. And actually I don't have another case in mind... ;-) – assylias Jul 07 '16 at 14:11
@AndyTurner It was also useful on older JVM when using substring to avoid keeping reference to the original string. Not the case since Java 7u6. http://stackoverflow.com/questions/27632533/is-it-redundant-to-create-a-new-string-for-a-substring-of-another-string – assylias Jul 07 '16 at 14:24
@assylias but that isn't really relevant when creating `String` objects from a **literal**. – Jesper Jul 07 '16 at 14:25
@assylias thanks. I agree with the oddness caveat... – Andy Turner Jul 07 '16 at 14:29

when to go for new string instead of string literal in java

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