[Java] Primitive Data Type & Wrapper

1. Package
   The package for wrapper is java.lang.
   
2. Wrapper Objective
   
   • Transform primitive type to/from string
   • Defined some useful constants for primitive type
     
   • Defined some useful methods for primitive type
     
3. Number
   It is the parent class of wrapper classes.
4. Primitive Data Type & Wrapper
1. Intege
• byte & Byte (8-bit)
• short & Short (16-bit)
• int & Integer (32-bit)
• long & Long (64-bit)
2. Float
• float & Float (32-bit)
• double & Double (64-bit)
3. char & Character (16-bit Unicode character)
   In Java, char is encoded in UTF-16
4. boolean & Boolean (ture or false)
5. void & Void
5. Primitive data type cast
   
6. Others
   
   • java.math.BigInteger & java.math.BigDecimal
     Defined useful math's methods for big(large) integer/decimal, such as abs, sin, cos, log, random, round.
     
   • Buffer
     Defined in package java.nio, it is used to handle a buffer of data.
     
     1. ByteBuffer
     2. ShortBuffer
     3. IntBufer
     4. LongBuffer
     5. CharBuffer
     6. FloatBuffer
     7. DoubleBuffer
        
   • xxx
     
7. xxx