Select Statement - Switch - select, statement, Switch

Select statement–switch

switch statement format:

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Execution process:

First calculate the value of the expression
Second, it is compared with case in turn. Once there is a corresponding value, the corresponding statement will be executed. During the execution, it will end when it encounters a break.
Finally, if all the cases do not match the value of the expression, the body of the default statement will be executed, and the program will end.

Execution flow chart

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Code example

public class Demo07Switch {

 public static void main(String[] args) {



 //Define variables to determine the day of the week

 int weekday = 6;

 //switch statement to achieve selection

 switch (weekday) {

 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("error");

 break;

}

}

}

Execution result

Precautions for using switch statement:

< p>1. The values after multiple cases cannot be repeated.

2. Only the following data types can be included in the parentheses after switch:

Basic data types: byte/short/char/int
Quotation Data type: String character string, enum enumeration

3. The format of the switch statement can be very flexible: the order can be reversed, and the break statement can also be omitted. “Which case is matched will be executed downwards from which position, until the break is encountered or the whole is over.”

The penetration of the case

In the switch statement, if break is not written after the case, penetration will occur, that is, the value of the next case will not be judged. Run directly backwards until a break is encountered, or the overall switch ends.

Execution flow chart

Code example

public class Demo07Switch {
public static void main(String[] args) {

//Define variables to determine the day of the week
int weekday = 6;
//switch statement to achieve selection
switch (weekday) {
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("error");
break;
}
}
}

Precautions for using switch statement:

2. Only the following data types can be included in the parentheses after switch:

Select Statement – Switch