1 import java.util.Scanner;
2
3 public class JiSuanQi {
4 public static void execute(int first_number, int second_number)
5 throws MyException {
6 // 手写异常不能让输入的数为负数
7 if (first_number < 0 || second_number < 0) {
8 throw new MyException("参数不能为负数");
9 }
10 }
11
12 public static void main(String[] args) {
13 for (;;) {
14 Scanner input = new Scanner(System.in);
15 System.out.println("请输入式子");
16 String shizi = input.nextLine();
17 String[] allfuhao = { "+", "-", "*", "/" };
18 jiSuan(shizi, allfuhao);
19
20 }
21 }
22
23 private static void jiSuan(String shizi, String[] allfuhao) {
24 for (int i = 0; i < allfuhao.length; i++) {
25 for (int j = 0; j < shizi.length(); j++) {
26 String fu = String.valueOf(shizi.charAt(j));
27 if (allfuhao[i].equals(fu)) {
28 try {
29 String first = shizi.substring(0, j);
30 Integer first_number = Integer.parseInt(first);
31 String second = shizi.substring(j + 1);
32 Integer second_number = Integer.parseInt(second);
33 execute(first_number, second_number);
34 if (i == 0) {
35 System.out.println(shizi + "="
36 + (first_number + second_number));
37 } else if (i == 1) {
38 System.out.println(shizi + "="
39 + (first_number - second_number));
40 } else if (i == 2) {
41 System.out.println(shizi + "="
42 + (first_number * second_number));
43 } else if (i == 3) {
44
45 System.out.println(shizi + "="
46 + (first_number / second_number));
47 }
48
49 } catch (MyException e) {
50 System.out.println("不允许使用负数");
51 } catch (NumberFormatException e) {
52 System.out.println("不是数字");
53 } catch (ArithmeticException e) {
54 System.out.println("除数不能为0");
55 }
56 return;
57 }
58
59 }
60
61 }
62 System.out.println("没找到运算符号，重新输入");
63 }
64 }
1 public class MyException extends Exception {
2
3 public MyException(){
4 super();
5 }
6 public MyException(String Exception ){
7 super(Exception);
8
9 }
10 }
