77-Integer serialized Java conventional method, Integer, int, String three mutual conversion, automatic packing, automatic unpacking

First, the methods commonly used on Integer

 

Package com.bjpowernode.java_learning; 


public  class D77_1_ { 

  public  static  void main (String [] args) { 

    Integer I1 = new new Integer (10 ); 

    // the type Integer type int 

    int I2 = i1.intValue (); 

    System.out.println (I2); 

    // important: static int parseInt (string s) into a digital string 

    int Age = the Integer.parseInt ( "25" ); 

    System.out.println (Age); 

    // int. price Integer.parseInt = ( "ABE"); // this statement will be successful programming, but are having problems running, parameters can only accept digital 

   

    // important: static double parseDouble (String s)

    Double D1 = Double.parseDouble ( ". 3" ); 

    System.out.println (D1); 

   

    // Static method: static String toBinaryString (int i) is converted into an integer i (string) binary returns 

    // static String toHexString (int i) convert to hex 

    // static String toOctalString (int i) to octal 

    System.out.println (Integer.toHexString ( 90 )); 

    System.out.println (Integer.toBinaryString ( 89 )); 

    System.out.println (Integer.toOctalString ( 89 )); 

   

    // convert one type or int type Integer String type: both methods, direct initialization; use Integer.valueOf () method 

    System.out.println (Integer. valueOf ( "45" )); 

    System.out.println (Integer.valueOf ( 45));

    System.out.println("=================================="); 

  }

}

2.Integer \ int \ String three types of conversion

 

    //int->Integer

    Integer i5 = Integer.valueOf(10);

   

    //Integer->int

    int i6 = i5.intValue();

   

    //String ->Integer

    Integer i7 = Integer.valueOf("10");

   

    //Integer ->String

    String s5 = i5.toString();

   

    //String -> int

    int i8 = Integer.parseInt("10");

   

    //int -> String

String s6 = 10 + "";

 

 

Second, automatic packing, automatic unpacking

1.JDK5.0 new features

The following properties are suitable after JDK1.5 version, including 1.5,

 

Package com.bjpowernode.java_learning; 


public  class D77_2_EncasementAutomatically { 

  public  static  void main (String [] args) { 

    // before JDK5.0 

    // INT-> packing Integer 

    Integer I1 = new new Integer (10 ); 

    // Integer -> int unpacking 

    int I2 = i1.intValue (); 

   

    // after JDK5.0, comprising 5.0 

    Integer I3 = 10; // autoboxing 

    int I4 = I3; // automatically unpacking 

    System.out.println (i3 ); 

    System.out.println (I4); 

   

    M1 ( 445);// autoboxing 

    System.out.println (M2 ( 85,50)); // first automatic packing, unpacking and then automatically 

  } 

  public  static  void M1 (Object O) { 

    System.out.println (O); 

  } 

  public  static  int M2 (I1 Integer, Integer I2) { 

    return I1- I2; 

  } 
}

2. In-depth auto-boxing and auto-unboxing

(1) Automatic boxing and unboxing is a conceptual automatic program compilation phase, independent and operating procedures;

(2) Automatic boxing and unboxing automatic main purpose is to facilitate programming.

Third, the source code:                                      

D77_1_IntegerAndIntAndStringTransform.java

D77_2_EncasementAutomatically.java

https://github.com/ruigege66/Java/blob/masterD77_1_IntegerAndIntAndStringTransform.java

https://github.com/ruigege66/Java/blob/master/D77_2_EncasementAutomatically.java

2.CSDN：https://blog.csdn.net/weixin_44630050

3. Park blog: https: //www.cnblogs.com/ruigege0000/

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