The basic syntax of java - selection structure

Java branch statement classification

Branch statement are selectively performed or skipped particular statement according to certain conditions, divided into two categories:

　　if-else statement
　　switch statement

 

if-else statement syntax

IF (boolean expression) { 
    statement or block of statements; 
} 
IF (boolean expression) { 
    statement or block of statements; 
} 
the else  IF (boolean expression) { 
    statement or block of statements; 
} the else { 
    statement or block of statements; 
}

if-else statement Application Example

 

Package com.uncleyong; 
 
public  class TestIf {
     public  static  void main (String [] args) {
         // if age <= 8, print "no school"
         // if age <= 14, prints out the "primary"
         // if age <= 17, print "junior high school"
         // If age <= 20, print "high school student"
         // If age <= 24, print "students"
         // if not met, print "graduate" 
 
        int Age = 5 ; 
 
        IF (Age <=. 8 ) { 
            System.out.println ( "no school" ); 
        } the else  IF (Age <= 14){
            System.out.println ( "primary" ); 
        } the else  IF (Age <=. 17 ) { 
            System.out.println ( "junior high school" ); 
        } the else  IF (Age <= 20 is ) { 
            System.out.println ( " High School " ); 
        } the else  IF (Age <= 24 ) { 
            System.out.println ( " Students " ); 
        } the else { 
            System.out.println ( " graduated " ); 
        } 
    } 
}

The switch statement syntax

Switch (expression) {
     Case constant 1: 
        sentence 1; 
        BREAK ;
     Case constant 2: 
        Statement 2; 
        BREAK ; 
    ...... 
    Case constant N: 
        Statement N; 
        BREAK ; 
    [ default : 
        statement; 
        BREAK ;] 
}

The switch statement Application examples

Package com.uncleyong; 
 
Import java.util.Scanner; 
 
public  class SwichScore {
     public  static  void main (String [] args) {
         / * 
            programming: the keyboard is read from a student performance, 
            is stored in the variable score according to the score value of the output corresponding grades: 
            score> = 90 level: a 
            70 = <score <90 level: B 
            60 = <score <70 level: C 
            score <60 level: D 
        * / 
        Scanner Scanner = new new Scanner (the System.in ); 
        System.out.print ( "Please enter student achievement, Score =" );
         int Score = scanner.nextInt();
 
        switch(score/10){
            case 10:
            case 9:
                System.out.println("A");
                break;
 
            case 8:
            case 7:
                System.out.println("B");
                break;
 
            case 6:
                System.out.println("C");
                break;
 
            default:
                System.out.println("D");
        }
 
    }
}

 

The switch statement relevant rules

　　switch (expression) of the expression of the return value must be one of several types: int, byte, char, short , enum, string;
　　value in the case clause must be constant, and all case clause value should be different;
　　default clause is optional;
　　BREAK statement is used after executing programs out of a case that the switch statement branch block;

 

 

Statement, article reproduced from the full-stack test notes https://www.cnblogs.com/UncleYong/p/9729156.html Thanks for sharing the power of God.