Wrapper class represented by Java integer

The integer of the Java species is the wrapper type of int

1. Integer is the wrapper type of int, the data type is class and the initial value is null

2. When initializing

　　

int i = 1new Integer (1);

3. Automatic packing and unpacking of class

1) Automatic packing

New Integer (1);    // using a normal declarative method Integer i = 1;    // using auto-boxing

2) Automatic Unpacking

Integer num = ten;      // Automatic Boxing System.out.print (num--);    // Automatic Unpacking

3) auto-unpacking and In-box to enjoy the Meta-mode

-128~128 (8bit Numeric) value, The memory will be reused after being boxed (that is, variables with different names 8bit numbers are the same in Memory)

A number other than -128~127, each declaration creates a new object, so the boxed object is not equal even if the unboxing value is the same (= = result is False)

4. The packaging classes in Java

1) Packing class is final type

2) Packaging class Support variable conversion

Byte	Java.lang.Byte
Boolean	Java.lang.Boolean
Short	Java.lang.Short
Char	Java.lang.Charactor
Int	Java.lang.Integer
Long	Java.lang.Long
Float	Java.lang.Float
Double	Java.lang.Double

5. Methods of the Integer class

1) Construction Method

Integer (int value)        // use number integer (string s)          // number represented by string

2) method

return value	Name	Function
Type conversions
Byte	Bytevalue ()	Returns a byte type
Double	Doublevalue ()	Returns a double type
Float	Floatvalue ()	...
Int	Intvalue ()
Long	Longvalue ()
Short	Shortvalue ()
String
String	ToString ()	A String object that represents the value
Static String	ToString (int I)	A String object that represents the specified integer
Static String	toString (int i, int radix)	An integer string object that represents the specified cardinality
Static String	Tobinarystring (int I)	Binary unsigned string
Static String	Tohexstring (int I)	Hexadecimal unsigned string
Static String	Tooctalstring (int I)	Octal unsigned string
static int	parseint (String S)	Convert a string to an integer
static int	Reverse (int I)	Reverse the order of the bits of the twos complement
static int	Rotateleft ()	Loop left Shift
static int	Rotateright ()
Int	Hashcode ()	Return hash code
Int	CompareTo (Integer)	Compare the values of two Integerd

Wrapper class represented by Java integer