Java's select statement

also known switch statement select statement, the following format

The switch statement format:

Implementation process

1. First, calculate the value of the expression
2. 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.
3. 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.

 

Code execution flow as shown below

 Code Example

Package demo03_Switch; 

public  class Demo01Switch {
     public  static  void main (String [] args) {
         // definition of variables, of the week is determined 
        int WEEKDAY =. 1 ;
         // Switch statement to achieve select 
        Switch (WEEKDAY) {
             Case . 1 : 
                the 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("错误");
                break;

        }
    }
}

The result of code execution

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. case of penetration : in a switch statement, if the latter case is not writing break, will appear penetration phenomenon, which is not a value judgment in the case, run directly back, until it encounters a break, or the entire switch End. Because of penetrating case, you must write on the break.