Wrapper class

All the wrapper classes (Integer, Long, Byte, Double, Float, Short) are subclasses of the abstract class Number. The object of the wrapper class contains or wraps its respective primitive data type.

Methods: xxxValue(): Returns the xxx value of this xxx object. compareTo(): equals(): valueof(String s): Returns a xxx object holding the double value represented by the argument string. parsexxx(String s): 同上。 toString():