Purpose of String.intern() in java

Question

Anyone Know purpose of String.intern() using java programming...

If i use intern what is the difference between ordinary string and string.intern()

This is a great thread explaining the same: http://stackoverflow.com/questions/1855170/when-should-we-use-intern-method-of-string-on-string-constants — sanket, Dec 11 '13 at 07:17
See [`String#intern`](http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#intern%28%29) — Justin, Dec 11 '13 at 07:18
Please refer this link. You can get good idea http://stackoverflow.com/questions/1091045/is-it-good-practice-to-use-java-lang-string-intern — Murali, Dec 11 '13 at 07:22
even this (http://stackoverflow.com/questions/1855170/when-should-we-use-intern-method-of-string-on-string-constants) — dev2d, Dec 11 '13 at 07:23
There are two suggestions to close this question as of now, but both suggestions state that it is a duplicate of questions that refer to using intern on string literals. This is a broader question, not a duplicate of these. — Jules, Dec 11 '13 at 07:31

rachana · Answer 1 · 2013-12-11T08:58:22.697

1

string interning is a method of storing only one copy of each distinct string value, which must be immutable. Interning strings makes some string processing tasks more time- or space-efficient at the cost of requiring more time when the string is created or interned. The distinct values are stored in a string intern pool.

Also read String pooling

edited Dec 11 '13 at 08:58

answered Dec 11 '13 at 07:19

rachana

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Aniket Thakur · Answer 2 · 2013-12-11T07:27:23.367

Interned String are stored in String pool rather than on general heap space. Prior to Java 7 this pool was in permgen area but from java 7 it has been moved to heap to prevent java.lang.OutOfMemoryError: PermGen space error which leds to JVM crash.

To summarize interned string with same text(.equals() returns true) will point to same object in string pool i.e even == operation will give true. Normal Strings created with new() with same content(.equals() returns true) will give false to == operation as they point to two different objects.

You may want to go through a good article Busting java.lang.String.intern() Myths . I am sure it will clear most of your doubts(Article also contains Java examples you can execute to see the results yourself).

Purpose of String.intern() in java

2 Answers2