指定抛出IOException

Question

有人能帮我解决我的问题吗。我是Java编程的初学者。以前，当我没有声明抛出IOException时，它给了我一个错误：

线程"main“java.lang.RuntimeException中的异常:不可编译的源代码-未报告的异常java.io.IOException；必须捕获或声明抛出

该方案如下：

import java.io.*;

public class addition {
    public static void main(String array[])throws IOException
    {
        InputStreamReader i = new InputStreamReader(System.in);
        BufferedReader b = new BufferedReader(i);
        System.out.println("Enter first number : ");
        int a1 = Integer.parseInt(b.readLine());
          System.out.println("Enter second number : ");
        int a2 = Integer.parseInt(b.readLine());
        int sum = a1 + a2 ;
        System.out.println("addition"+sum);
    }

}

Answer 1

如果在尝试从输入流读取时出现I/O故障，BufferedReader函数readLine()将抛出一个IOException。在Java中，如果出现异常，必须使用try catch语句来处理它们：

import java.io.*;

public class addition {
public static void main(String array[])throws IOException
{
    InputStreamReader i = new InputStreamReader(System.in);
    BufferedReader b = new BufferedReader(i);
    System.out.println("Enter first number : ");

    // Attempt to read in user input.
    try {
        int a1 = Integer.parseInt(b.readLine());
        System.out.println("Enter second number : ");
        int a2 = Integer.parseInt(b.readLine());
        int sum = a1 + a2 ;
        System.out.println("addition"+sum);
    }

    // Should there be some problem reading in input, we handle it gracefully.
    catch (IOException e) {
        System.out.println("Error reading input from user. Exiting now...");
        System.exit(0);
    }
}
}