8bit 1byte byte
16bit 2byte short
32bit 4byte int
64bit 8byte long
http://docs.oracle.com/javase/specs/jls/se8/html/jls-4.html#jls-4.2.1
The values of the integral types are integers in the following ranges:
For long, from -9223372036854775808 to 9223372036854775807, inclusive
For char, from ‘\u0000‘ to ‘\uffff‘ inclusive, that is, from 0 to 65535
0x0000 - 0xffff 0-65535
0x0000 - 0xFFFF 0-65535
原文：http://www.cnblogs.com/zno2/p/4629973.html