Java基础笔记11——while和do_while
1.while规则:
while(表达式)
{
语句块;
}
(1)判断表达式
(2)当表达式为真,重复执行语句块,直到表达式为假,跳出循环
2.do...while规则:
do{
语句块;
}while(表达式);
(1)执行语句块
(2)判断表达式;当表达式为真,重复执行语句块,直到表达式为假,跳出循环
3.while和do...while区别
(1)while:先判断表达式,再执行语句块
(2)do...while:先执行一次语句块,再判断表达式
4.死循环(表达式一直为真时,即可陷入死循环)
while(true){
语句块;
}
package com.lqh.chapter01; public class _08while_dowhile { public static void main(String[] args) { //while int i = 0; int sum = 0; while (i <= 100) { sum += i; i++; } System.out.println("---while---"); System.out.println("1+2+3+...+100="+sum); //do...while i = 0; sum = 0; do { sum +=i; i++; }while(i <= 100); System.out.println("---do...while---"); System.out.println("1+2+3+...+100="+sum); i = 0; sum = 0; //死循环 while(true) { if(i <= 100) { sum += i; i++; } else { break;//当i>100跳出死循环 } } System.out.println("---死循环---"); System.out.println("1+2+3+...+100="+sum); } }
输出结果为:
---while---
1+2+3+...+100=5050
---do...while---
1+2+3+...+100=5050
---死循环---
1+2+3+...+100=5050