プログラム制御文

プログラミング言語は、制御文を使用して実行フローを生成し、プログラム順序実行やブランチ実行などのプログラム状態の変更を完了します.
if else

// Demonstrate if-else-if statements. 
class IfElse { 
    public static void main(String args[]) { 
        int month = 4; // April 
        String season; 
 
        if(month == 12 || month == 1 || month == 2) 
            season = "Winter"; 
        else if(month == 3 || month == 4 || month == 5) 
            season = "Spring"; 
        else if(month == 6 || month == 7 || month == 8) 
            season = "Summer"; 
        else if(month == 9 || month == 10 || month == 11) 
            season = "Autumn"; 
        else 
            season = "Bogus Month"; 
 
        System.out.println("April is in the " + season + "."); 
    } 
} 

switch case

// A simple example of the switch. 
class SampleSwitch { 
    public static void main(String args[]) { 
        for(int i=0; i<6; i++) 
            
        switch(i) { 
            case 0: 
                System.out.println("i is zero."); 
                break; 
            case 1: 
                System.out.println("i is one."); 
                break; 
            case 2: 
                System.out.println("i is two."); 
                break; 
            case 3: 
                System.out.println("i is three."); 
                break; 
            default: 
                System.out.println("i is greater than 3."); 
        } 
    } 
} 

while

// Demonstrate the while loop. 
class While { 
    public static void main(String args[]) { 
        int n = 10; 
 
        while(n > 0) { 
            System.out.println("tick " + n); 
            n--; 
        } 
    } 
} 

do while

// Demonstrate the do-while loop. 
class DoWhile { 
    public static void main(String args[]) { 
        int n = 10; 
 
        do { 
            System.out.println("tick " + n); 
            n--; 
        } while(n > 0); 
    } 
} 

for

// Using the comma. 
class Comma { 
    public static void main(String args[]) { 
        int a, b; 
 
        for(a=1,  b=4; a<b; a++ ,  b--) { 
            System.out.println("a = " + a); 
            System.out.println("b = " + b); 
        } 
    } 
} 

break

// Using break with nested loops. 
class BreakLoop3 { 
    public static void main(String args[]) { 
        for(int i=0; i<3; i++) { 
            System.out.print("Pass " + i + ": "); 
            for(int j=0; j<100; j++) { 
                if(j == 10) break; // terminate loop if j is 10 
                System.out.print(j + " "); 
            } 
            System.out.println(); 
        } 
        System.out.println("Loops complete."); 
    } 
} 

continue

// Demonstrate continue. 
class Continue { 
    public static void main(String args[]) { 
        for(int i=0; i<10; i++) { 
            System.out.print(i + " "); 
            if (i%2 == 0) continue; 
            System.out.println(""); 
        } 
    } 
}