BMI指数

た入场券 2024-03-31 11:13 71阅读 0赞

**1** **问题**

If-else与Switch都可以作为条件语句，但其用法有一定不同。

**2** **方法**

首先给定一个让用户输入成绩的Scanner语句，判断学生成绩分别在1-5各个情况不同的输出。分别使用if-else和Switch运行，观察语句使用的区别。

**当if-else运行时：**

![4f252a332d27018ba5b4e824c0c219af.png][]

**当Switch运行时：**

![3306ce2bd855d0163ffc7c8d67064ebd.png][]

<table> 
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 <td>当Switch运行时的代码： package homework; import java.util.Scanner; public class W1b2 { public static void main(String[] args) { &nbsp; &nbsp; &nbsp; &nbsp;Scanner scanner = new Scanner(System.in); System.out.println("请输入学生成绩:"); &nbsp; &nbsp; &nbsp; &nbsp;int score = scanner.nextInt(); &nbsp; &nbsp; &nbsp; &nbsp;switch (score){ case 1: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("不及格"); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;break; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;case 2: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("及格"); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;break; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;case 3: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("中等"); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;break; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;case 4: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("良好"); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;break; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;case 5: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("优秀"); &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;break; } &nbsp; } }</td> 
 </tr> 
 <tr> 
 <td>当if-else运行时的代码： package homework; import java.util.Scanner; public class W1b { public static void main(String[] args) { &nbsp; &nbsp; &nbsp; &nbsp;Scanner scanner = new Scanner(System.in); System.out.println("请输入学生成绩:"); &nbsp; &nbsp; &nbsp; &nbsp;int score = scanner.nextInt(); &nbsp; &nbsp; &nbsp; &nbsp;if (score == 1){ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("不及格"); } if (score == 2){ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("及格"); } if (score == 3){ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("中等"); } if (score == 4){ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("良好"); } if (score == 5){ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;System.out.println("优秀"); } &nbsp; &nbsp;} }</td> 
 </tr> 
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 <td></td> 
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 </tbody> 
</table>

**3** **结语**

If-else与的区别：

1.if可以用于判断数值，也可以判断区间，当匹配到if里的值会直接输出结束。  
2.switch用于对固定的几个值进行判断，判断的值的类型有限，当匹配到case的值会使用break停止。

[4f252a332d27018ba5b4e824c0c219af.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/460fea9f5879449882ee82f7734dd091.png
[3306ce2bd855d0163ffc7c8d67064ebd.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/60c03b86c6ad4b74b12d71d64d80efc9.png