Java中几种常见的循环

多重if_else:

package com.dengchaoqun.ht;

public class Double_For02 {
	/**
	 * 
	 * 打印乘法表
	 */
	public static void main(String[] args) {
		for (int i = 1; i < 10; i++) {
			for (int j = 1; j <= i; j++) {
				int a = i * j;
				System.out.print(i + "*" + j + "=" + a + "\t");
			}
			System.out.println();
		}
	}

}

　　

switch_case:

package com.dengchaoqun.ht;
import java.util.Scanner;
public class Leap_yearOrCommon_year {
	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		int year;
		int month;//用来输入月份
		System.out.println("请输入年份：");
		year=scan.nextInt();
		System.out.println("请输入月份：");
		month=scan.nextInt();
		//判断是否为闰年
		if((year%4==0&&year%100!=0)||(year%400==0))
		{
			System.out.println(year+"年是闰年！");
		}
		else
		{
			System.out.println(year+"年是平年！");
		}
		//输出月份的天数
		switch(month)   //switch-case语句输出月份的天数
		{
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12:
			System.out.println(year+"年"+month+"月是31天！");
			break;
		//判断是否是闰年的二月还是平年的二月
		case 2:
			if((year%4==0&&year%100!=0)||(year%400==0))
			{
				System.out.println(year+"年"+month+"月是29天！");
				break;
			}
			else
			{
				System.out.println(year+"年"+month+"月是28天！");
				break;
			}
		case 4:
		case 6:
		case 9:
		case 11:
			System.out.println(year+"年"+month+"月是30天！");
			break;
		default:
			System.out.println("请输入正确的年份和月份！");
		}
		scan.close();
	}
}

　　

while:

package com.dengchaoqun.ht;

public class While {
/**
 * 
 * 使用while单循环求1！+2！+...+7！
 */
	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		int i=1;
		int j=1;
		int sum=0;
		while(i<8)
		{
			j=i*j;
			sum+=j;
			i++;
		}
		System.out.println("1！+2！+...+7！="+sum);

	}

}

　　

do_while:

package com.dengchaoqun.ht;

import java.util.Scanner;

public class Do_while_02 {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		Scanner scan = new Scanner(System.in);
		do {
			int n = 0;
			System.out.println("1.注册");
			System.out.println("2.登录");
			System.out.println("0.退出");
			System.out.println("请选择输入项：");
			n = scan.nextInt();
			if (n == 0) {
				System.out.println("您选择了退出");
				break;
			} else if (n == 1) {
				System.out.println("您选择了登录");
			} else if (n == 2) {
				System.out.println("您选择了退出");
			} else {
				System.out.println("您选择了错误");
			}
		} while (true);
		scan.close();

	}

}

　　

for:

package com.dengchaoqun.ht;

public class Double_For02 {
	/**
	 * 
	 * 打印乘法表
	 */
	public static void main(String[] args) {
		for (int i = 1; i < 10; i++) {
			for (int j = 1; j <= i; j++) {
				int a = i * j;
				System.out.print(i + "*" + j + "=" + a + "\t");
			}
			System.out.println();
		}
	}

}