Returns a canonical representation for the string object.
A pool of strings, initially empty, is maintained privately by the
When the intern method is invoked, if the pool already contains a
string equal to this
String object as determined by
equals(Object) method, then the string from the pool is
returned. Otherwise, this
String object is added to the
pool and a reference to this
String object is returned.
It follows that for any two strings
s.intern() == t.intern() is
if and only if
All literal strings and string-valued constant expressions are interned. String literals are defined in section 3.10.5 of the The Java™ Language Specification.