How to implement loop in java

Java is a sequential structure program that can only be executed once. If you want to perform the same operation multiple times, you need to use a loop structure.

There are three main loop structures in Java:

• while loop

• do...while loop

• for loop

Introducing an enhancement mainly for arrays in java5 type for loop.

1. while loop

while is the most basic loop, its structure is:

package com.example.lesson1;

//while（布尔（true/false）表达式）{
//循环内容 
//只要布尔表达式为 true 循环体就会一直执行下去。

//来看看实例吧:
public class Test {
    public static void main(String args[]) {
        int x = 10;
        while (x < 20) {
            System.out.print("value of x :" + x);
            x++;
            System.out.print("\n");
        }
    }
}

2. do...while loop

For the while statement, if the condition is not met, the loop cannot be entered. But sometimes we need to execute it at least once even if the conditions are not met.

do…while loop is the same as while loop. The difference is that

do…while loop will be executed at least once.

package com.example.lesson1;

//do{
//  //代码语句
//  }while（布尔值表达式）；

//  注意：布尔表达式在循环体的后面，所以语句块在检测布尔表达式之前已经执行了。如果布尔表达式值为true，则语句块
//一直执行，直到布尔表达式的值为false。

//  实例:
public class Test {
    public static void main(Staing args[]) {
        int x = 10;
        do {
            System.out.print("value of x :" + x);
            x++;
            System.out.print("\n");
        } while (x < 20);
    }
}

3. for loop

Although all loop structures can be expressed by while or do...while, java provides another statement (for loop), Made some loop structures simpler.

for循环执行的次数是在执行前就确定的。语法格式如下:
    //for (  1初始化;  2布尔表达式; 4更新){
            3//代码语句
    //}

    //关于for循环有以下几点说明：
    //1，最先执行初始化步骤。可以声明一种类型，但可初始化一个或多个循环控制变量，也可以是空语句。
    //2，然后，检测布尔表达式的值。如果是true，循环体被执行，如果是false，循环体终止，开始执行循环后面的语句。
    //3，执行一次循环后，更新循环控制变量。
    //4，再次检测布尔表达式。循环执行上面的过程。

    public class Test{
        public static void main (Staing args[ ]){
        for(int x=10;x<20;x=x+1){
        System.out.print("value of x :"+x);
        System.out.print("\n");
                }
            }
    }

4. java enhanced for loop

java5 introduces an enhanced rot loop mainly used for arrays.

java enhanced for loop syntax format is as follows:

or(声明语句：表达式){
        //代码句子
    }

//声明语句：声明新的局部变量，该变量的类型必须和数组元素的类型匹配。其作用域限定在循环语句块
//其值与此时数组元素的值相等。
//表达式：表达式是要访问的数组名，或者是返回值为数组的方法。

//实例：
public class test {
    public static void main(String args[]) {
        int[] numbers = { 10, 20, 30, 40, 50 };
        for (int x : numbers) {
            System.out.print(x);
            System.out.print(",");
        }
        System.out.print("\n");
        String[] names = { "James", "Larry", "Tom", "Lacy" };
        for (String name : names) {
            System.out.print(name);
            System.out.print(",");
        }
    }
}

The above is the detailed content of How to implement loop in java. For more information, please follow other related articles on the PHP Chinese website!