Wrapper class

- The class wraps primitive type. - When handle 8 types of primitive type as object. =>why? OOP is Object-Oriented Programming. It needs to be as Object. 90% is Object and remains are primitive type because of performance.

public final class Integer extends Number implements Comparable {
    ...
    private int value;//wraps int type.
}

primitive type	wrapper class	constructor	example
boolean	Boolean	Boolean(boolean value) Boolean(String s)	Boolean b = new Boolean(true); Boolean b2 = new Boolean("true");
char	Character	Character(char value)	Character c = new Character('a');
byte	Byte	Byte(byte value) Byte(String s)	Byte b = new Byte(10); Byte b2 = newByte("10");
short	Short	Short(short value) Short(String s)	Short s = new Short(10); Short s2 = new Short("10");
int	Integer	Integer(int value) Integer(String s)	Integer i = new Integer(100); Integer i2 = new Integer("100");
long	Long	Long(long value) Long(String s)	Long l = new Long(100); Long l2 = new Long("100");
float	Float	Float(double value) Float(float value) Float(String s)	Float f = new Float(1.0); Float f = new Float(1.0f); Float f = new Float("1.0f");
double	Double	Double(double value) Double(String s)	Double d = new Double(1.0); Double d = new Double("1.0");

Integer i = new Integer(100);//address : 0x100
Integer i2 = new Integer(100);//address : 0x200

System.out.prinln("i==i2?" + (i==i2));//false.0x100!=0x200
System.out.prinln("i.equals(i2)?" + i.equals(i2));//true.means overriding.
//오른쪽 값이 더 작으면 양수,오른쪽 값이 더 크면 음수, 같으면 0
System.out.prinln("i.compareTo(i2) ="+i.compareTo(i2)); 
System.out.prinln("i.toString()="+i.toString());