2020-12-03条件判断/while、switch语句/do while 循环/for循环

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我是靠谱客的博主寒冷百合，最近开发中收集的这篇文章主要介绍2020-12-03条件判断/while、switch语句/do while 循环/for循环，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

if else 条件

import java.util.Scanner;

public class TestIf{
	static final int CH_AGE = 18;
	static Scanner inScanner = new Scanner(System.in);
	public static void main(String []args){
		int age = 12;
		System.out.println("请输入您的年龄回车继续");
		age = inScanner.nextInt();

	if(age < CH_AGE){//未成年
		System.out.println("您是未成年人")
		}else{
			System.out.println("您满足大于等于"+CH_AGE+"岁，是成年人");
			}
	}
}

if else if复杂条件

import java.util.Scanner;

public class TestIfElseIf{
	static Scanner inScanner = new Scanner(System.in);
	public static void main(String []args){
		double score = inScanner.nextDouble();
		
		if(score >= 0 && score <= 100){
			if(score >= 90){
				System.out.println("成绩优秀");
			}else if(score >=80){
				System.out.println("成绩良好");
			}else if(score >=70){
				System.out.println("成绩中等");
			}else if(score >= 60){
				System.out.println("成绩及格");
			}else{
				System.out.println("成绩不及格");
			}
		}else{
			System.out.println("分数不合法，必须位于0-100之间")
			}
		
	}
}

条件表达式

(三目运算符)

import java.util.Scanner;
public class TestConditionPer{
	static Scanner inScanner = new Scanner(System.in);
	public static void main（String []args）{
		String message = "";
		int age = 0;
		System.out.println("请输入您的年龄回车继续");
		age = inScanner.nextInt;
		System.out.println(age >= 18 ? "成年人" ： "未成年人");
		message = age < 18 ? "未成年人" : "成年人"；
		System.out.println(message);
	}
}

switch语句

import java.util.Scanner;
public class TestSwitch{
	static Scanner inScanner = new Scanner(System.in);
	public static void main(String []args){
		System.out.println("请输入1-3之间的一个整数回车继续");
		int num = inScanner.nextInt();
		System.out.println("请输入年龄回车继续");
		int age = inScanner.nextInt();
		String mess = "";
		switch(num){
			case 1:
				System.out.println("您是中国国籍");
				mess = age > 18 ? "成年人" : "未成年人";
				System.out.println(mess);
				break;
			case 2:
				System.out.println("您是美国国籍");
				mess = age > 18 ? "成年人" : "未成年人";
				System.out.println(mess);
			case 3:
				System.out.println("您是日本国籍");
				mess = age > 18 ? "成年人" : "未成年人";
				System.out.println(mess);
			default:
				System.out.println("您是除中、美、日国籍外的人");
		}  
	}
}

while循环

public class TestWhile{
	public static void main(String []args){
		//1到100正整数累加
		num = 1;
		sun = 0;
		while(num <= 100){
			sun += num;
			num++;
		}
		System.out.println("1到100正整数累计的结果是"+sum);


		//使用嵌套循环完成10*10的正方形图形输出
		int line = 1;
		while(line <= 10){
			int num1 = 1;
			whlie(num1 <= 10){
				System.out.println("□");
				num1++;
			}
			System.out.println("n");//在内层循环完成10次后换行
			line++;
		}
	}
}

do whlie 循环

import java.util.Random;
import java.util.Scanner;

public class TestDoWhile {
	static Scanner in = new Scanner(System.in);
	
	public static void main(String[] args) {
		Random random = new Random();//创建生成随机数的工具对象
		int num = 0;//存储用户输入所猜的数
		
		String succMmess = "☺";
		String failMmess = "☹";
		boolean bool = true;
		do {
			int suiji = random.nextInt(5);//生成小于5的随机整数
			System.out.println("请输入0-4之间的整数看看您能不能猜对");
			num = in.nextInt();//接收用户输入的数
			if (num == suiji) {//猜对了
				bool = false;
				System.out.println("恭喜您，猜对了"+succMmess);
			}else {//猜错了
				bool = true;
				System.out.println("对不起猜错了，随机数是"+suiji+"请重新猜"+failMmess);
			}
		} while (bool);

	}

}

for循环

import java.util.Scanner;
/**
 * 使用for循环控制用户银行卡密码输入次数
 * 第二次输入密码错误后提醒用户再次输入错误将锁定银行卡
 * 如果第三次密码输入错误则锁定银行卡
 * @author Administrator
 *
 */
public class ForLoopDemoTwo {

	public static void main(String[] args) {
		Scanner inScanner = new Scanner(System.in);
		int password = 123456;//银行卡密码
		boolean locked = false; 
		for (int i = 1; i <= 3; i++) {
			
			System.out.println("请输入您的银行卡密码");
			int useword = inScanner.nextInt();
			
			if(useword == password) {
				System.out.println("密码正确，请继续……");
				i = 4;
			}else {
				if(i ==1) {
					System.out.println("这是您第1次错误，还有2次机会");
				}else if (i ==2){
					System.out.println("这是您第2次错误，第三次错误将锁定银行卡");
				}else if (i ==3) {
					System.out.println("密码错误3次，银行卡已被锁定");
					locked = true;
				}
			}
		
			
		}

	}

}