Java流程控制06：While循环详解

 一、while循环

public class WhileDemo01 {
    public static void main(String[] args) {

        //输出1~100,并且求和
        int i = 1;
        int sum = 0;
        while(i != 101){
            System.out.println(i);
            sum=sum+i;
            i++;
        }
        System.out.println(sum);
    }
}

二、DoWhile循环

public class WhileDemo01 {
    public static void main(String[] args) {

        //输出1~100,并且求和
        int i = 1;
        int sum = 0;
        do{
            System.out.println(i);
            sum=sum+i;
            ++i;
        }while(i<=100);
        System.out.println(sum);
    }
}

public class WhileDemo02 {
    public static void main(String[] args) {
        int a = 0;
        while(a<0){
            System.out.println(a);
            a++;
        }
        System.out.println("======================");
        do{
            System.out.println(a);
            a++;
        }while(a<0);
    }
}//输出0

三、for循环

public class ForDemo01 {
    public static void main(String[] args) {
        //练习一：计算0-100之间奇数和偶数的和
        int oddsum = 0;
        int evensum = 0;
        for(int i = 0;i <100;i++){
            if(i % 2 == 1){
                oddsum = oddsum + i;
            }else{
                evensum = evensum + i;
            }
        }
        System.out.println("奇数和："+oddsum+"偶数和："+evensum);
    }
}

public class ForDemo02 {
    public static void main(String[] args) {
        //练习二：用while或者for循环输出1-1000之间能被5整除的数，并且每行输出3个。

        for(int i = 0;i <= 1000;i++){
            if(i % 5 == 0){
                System.out.print(i+"\t");//把println换成print，println输出完会换行，print输出完不会换行
            }
            if(i % (5 * 3) == 0){
                System.out.println("\n");//也可以是System.out.println();
            }
        }
    }
}

public class ForDemo03 {
    public static void main(String[] args) {
        //打印九九乘法表
        for(int i = 1;i <=9;++i){
            for(int j = 1;j <=i;j++){
                System.out.print(j+"*"+i+"="+j*i+"\t");
            }
            System.out.println();
        }
    }
}