Several looping methods in Java

This article mainly introduces several loop methods in java, so that everyone can have more knowledge about loop structures. Understanding allows everyone to be more comfortable in the learning process without reporting bugs.

1. for loop

for loop is the most commonly used loop method in java and its structure Is:

for (initialization; Boolean expression; update condition) {

          Loop body code

}

实例：1到100的和？
public class Test{
    public static void main(String[] args){
        int n=0;
        for(int i=1;i<=100;i++){
            n=n+i;
        }
        System.out.println(n);
    }
}

实例：嵌套循环，九九乘法表
public class Test{
    public static void main(String[] args){
        //后执行外循环
        for(int i=1;i<=9;i++){
            //先执行内循环
            for(int j=1;j<=i;j++){
                Systeam.out.print(j+"*"+i+"="+i*j+" ");
            }
            System.out.println();
        }
    }
}

2.while loop

The while loop is mainly used when the number of loops is unknown. Its structure is:

while(Boolean expression){

Loop body code


}


实例：1到100的和？
public class Test{
    public static void main(String[] args){
        int j=0;
        int i=1;
        int n=101;
        //如果i<n为true就会一直循环下去
        while(i<n){
            j=j+i;
            i++;
        }
        System.out.println(j);
    }
}

3.do...while loop

do...while loop is similar to while loop, but different It is a Boolean expression that will execute the loop code at least once even if there is an error. Its structure is:

do{

Loop body code


}while(Boolean expression Formula)

实例：1到100的和？
public class Test{
    public static void main(String[] args){
        int j=0;
        int i=1;
        int n=101;
        do{
            j=j+i;
            i++;
        }while(i<n);
        System.out.println(j);
    }
}

4. Enhanced for loop

After Java5, a loop mainly used for arrays was introduced. Its structure is:

for (Declaration statement: expression) {

/* Declaration statement: Declare a new local variable. The type of the variable must match the type of the array element. Its scope is limited to the loop statement block, *its value is equal to the value of the array element at this time.

* Expression: The expression is the name of the array to be accessed, or a method that returns an array. */

# Circulation code

}


实例:数组循环
public class Test{
    public static void main(String[] args){
        int[] num={1,3,5,6,8,};
        for(int x : num){
            System.out.print(x+",");
        }
        String[] color={"红","黄","蓝","绿","紫"};
        for(String name : color){
             System.out.print(name+",");
        }
    }
}

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