Java - Loop Control 循环控制

Java - Loop Control 循环

循环控制体

NO.	Loop
1	while loop
2	for loop
3	do...while loop

1、while loop

Java While Loop

Example:

public class TestWhile {
    public static void main(String[] args) {
        int x = 10;
        while (x < 20) {
            System.out.println(x);
            x++;
        }
    }
}

output:

10
11
12
13
14
15
16
17
18
19

2、for loop

java_for_loop.jpg

Example

public class TestFor {
    public static void main(String[] args) {
        int persons[] = {1, 2, 3, 4, 5, 6};

        // case 1
        System.out.println("第一种用法");
        for (int i = 0, len = persons.length; i < len; i++) {
            System.out.println(persons[i]);
        }

        // case 2
        System.out.println("第二种用法");
        for (int person : persons) {
            System.out.println(person);
        }
    }
}

output

第一种用法
1
2
3
4
5
6
第二种用法
1
2
3
4
5
6

3、do...while loop

java_do_while_loop.jpg

Example

public class TestDo {
    public static void main(String[] args) {
        int x = 10;
        do {
            System.out.println(x);
            x++;
        } while (x < 20);
    }
}

Output

10
11
12
13
14
15
16
17
18
19

Break Statement in Java

1、break

直接跳出循环

java_break_statement.jpg

Example

public class TestBreak {
    public static void main(String[] args) {
        int arr[] = {10, 20, 30};

        for(int n : arr) {
            if (n == 30) {
                break;
            }
            System.out.println(n);
        }
    }
}

Output

10
20

2、continue

跳出当前循环，直接下一个循环

java_continue_statement.jpg

Example

public class TestContinue {
    public static void main(String[] args) {
        int numbers[] = {10,20,30,40};

        for(int number : numbers){
            if(number == 20){
                continue;
            }
            System.out.println(number);
        }
    }
}

Output

10
30
40