When should we use intern method of String on String literals

Question

According to String#intern(), intern method is supposed to return the String from the String pool if the String is found in String pool, otherwise a new string

Answer 1

Interned Strings avoid duplicate Strings. Interning saves RAM at the expense of more CPU time to detect and replace duplicate Strings. There is only one copy of each String that has been interned, no matter how many references point to it. Since Strings are immutable, if two different methods incidentally use the same String, they can share a copy of the same String. The process of converting duplicated Strings to shared ones is called interning.String.intern() gives you the address of the canonical master String. You can compare interned Strings with simple == (which compares pointers) instead of equals which compares the characters of the String one by one. Because Strings are immutable, the intern process is free to further save space, for example, by not creating a separate String literal for "pot" when it exists as a substring of some other literal such as "hippopotamus".

To see more http://mindprod.com/jgloss/interned.html