java - 如何解决这些错误

Question

我有一个用 Java 编写的程序，可以将 2 个数字相加并输出总和。 (数字通过键盘输入)。但是，我有一个错误需要帮助解决。我将在代码后面解释错误:

package com.sigma.java7;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Addition {

    public static void main(String[] args) throws IOException {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    do {
        try {
           System.out.println("Enter A :");
           String numA = br.readLine();
           int a = Integer.parseInt(numA);
           break;
        } catch (Exception e) {
           System.out.println("Incorrect input. Please enter an integer.");
        }
    } while (true);
    do {
        try {
           System.out.println("Enter B :");
           String numB = br.readLine();
           int b = Integer.parseInt(numB);
           break;
        } catch (Exception e) {
           System.out.println("Incorrect input. Please enter an integer.");
        }
    } while (true);
    System.out.println("The sum of the numbers is: " +(a+b));
    br.close();
  }
}

在行

"System.out.println("The sum of the numbers is: " +(a+b));" 

我收到错误:“a 无法解析为变量，b 无法解析为变量。”为什么？

Answer 1

你的变量范围很糟糕。当您定义局部变量时，它只能在同一个 block 中工作。例如。

{
    int i = 2;
    {
       int k = 4;
       // i can be accessed here.
    }
    // i can be accessed here.
    // k can not be accessed here.    
}