编辑代码

import java.util.*;
public class HelloWorld {
    public static void main(String []args) {
        System.out.println("Hello World!，这是一个简单计算器");
        try{
            Scanner sc = new Scanner(System.in);
            Double a = sc.nextDouble();
            String b = sc.next();
            Double c = sc.nextDouble();
            sc.close();
            Double result = 0.0;
            switch(b){
                case "+" :
                    result = a+c; 
                    break;
                case "-" :
                    result = a-c;
                case "*" :
                    result = a*c;
                    break;
                case "/" :
                    result = a/c;
                    break;
                default :
                    System.out.println("请输入正确的计算符号！");
            }
            if(result != 0){
                System.out.println("计算结果："+result);
            }
        }catch(InputMismatchException e){
            System.out.println("请输入正确的算数表达,异常："+ e.getMessage());
        }catch(NoSuchElementException e){
            System.out.println("请在计算符号前后用空格隔开,异常："+ e.getMessage());
        }
    }
}