Self Java, day03_Java select statement switch

Select statement --switch

The switch statement format:
Implementation process
  • First, calculate the value of the expression
  • Secondly, compare and order case, if there is a corresponding value, will execute the corresponding statement in the process of implementation, it encounters a break will end.
  • Finally, if the case were all expressions and values ​​do not match, it will execute the default statement body part, and the program ends off.

Execution Flow

 

 

demand

Code illustrates basic use of the switch

public  class Demo07Switch {
     public  static  void main (String [] args) {
         // definition of variables, of the week is determined 
        int NUM =. 6 ;
         // Switch statement to achieve select 
        Switch (NUM) {
             Case . 1 : 
                System.out.println ( " Monday " );
                 BREAK ;
             Case 2 : 
                System.out.println ( " Tuesday " );
                 BREAK ;
             Case 3 : 
                System.out.println ( " Wednesday ");
                 BREAK ;
             Case 4 : 
                System.out.println ( "Thursday" );
                 BREAK ;
             Case 5 : 
                System.out.println ( "Friday" );
                 BREAK ;
             Case 6 : 
                System.out.println ( "Saturday" );
                 BREAK ;
             Case 7 : 
                System.out.println ( "Sunday" );
                 BREAK ;
             default: 
                System.out.println ( "Data unreasonable" );
                 break ; // the last break statement can be omitted, but it is strongly recommended not to omit 
        } 
    } 
}

Results of the

 

 

Note the use of the switch statement:

  • The latter case a plurality of values ​​can not be repeated.
  • Switch parentheses behind which only the following data types: basic data types: byte / short / char / int reference Data Type: String String, enum enum
  • The switch statement format can be very flexible: before and after the order can be reversed, and break statement can also be omitted. "Which case match on a position from which to perform downward until it encounters a break or a whole until the end."
  • In a switch statement, if the case does not write back break, will appear penetration phenomenon, which is not a value judgment in the case, run directly back, until it encounters a break, or the end of the whole switch. Because of penetrating case, therefore beginners when writing switch statement, you must write on the break. 
 
 

 

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Origin www.cnblogs.com/wurengen/p/11521041.html