The trim() method returns a new String with the leading and trailing whitespace removed.

String s = new String("   Hello World!!  ");
String t = s.trim();  // t = "Hello World!!"

If you trim a String that doesn’t have any whitespace to remove, you will be returned the same String instance.

Note that the trim() method has its own notion of whitespace, which differs from the notion used by the Character.isWhitespace() method:

• All ASCII control characters with codes U+0000 to U+0020 are considered whitespace and are removed by trim(). This includes U+0020 'SPACE', U+0009 'CHARACTER TABULATION', U+000A 'LINE FEED' and U+000D 'CARRIAGE RETURN' characters, but also the characters like U+0007 'BELL'.
• Unicode whitespace like U+00A0 'NO-BREAK SPACE' or U+2003 'EM SPACE' are not recognized by trim().