What is Unicode System in java ?

Unicode System  is a universal international standard  character encoding that is capable of representing most of the world's written languages.

Why java uses Unicode System?

Before Unicode,there were many language standards:
ASCII: (American Standard Code for Information  Interchange) for the United States.
ISO 8859-1:  for Western European Language.
KOI-8 : for Russian.
GB18030 and BIG-5:  for chinese, and so on.

This caused following two problems:
>1. A particular code value corresponds to different letters in the various language standards.
>2. The encodings for languages with large character sets have variable length.Some common                 characters are encoded as single bytes, other require two or  more byte.

To solve these problems, a new language standard was  developed i.e. Unicode System.
In unicode, character holds 2 byte, so java also uses  2 byte for characters.

lowest value in unicode system: \u0000
highest value in unicode system: \uFFFF