文件结尾NullPointerException [英] End of file NullPointerException

问题描述

我想要的是通过在命令行中输入<$ c $来达到 EOF ，方法是 Ctrl + z c> BufferedReader 从控制台读取。以下代码这样做。但是问题是，在达到 EOF 之后，它会发出 NullPointerException 。有没有办法跳过此异常？或者更确切地说，通过控制台读取 BufferedReader 达到 EOF 的正确方法是什么？

What I wanted is to reach EOF by typing Ctrl + z from command line with BufferedReader reading from console. The following code does so. But the problem is, it issues a NullPointerException after reaching EOF. Is there a way to skip this exception? Or more precisely, what is the proper way of reaching EOF with BufferedReader reading from console?

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

class EOF {

    public static void main(String args[]) {
        String s = "";
        String EOF = "^z";
        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
        try {
            while (!s.equals(EOF)) {
                s = read.readLine();   
            }
        } catch (IOException e) {} 
    }

}

推荐答案

或更准确地说，通过console.bufferedReader读取EOF的正确方法是什么？

Or more precisely, what is the proper way of reaching EOF with bufferedReader reading from console?

当前，您实际上正在检测字符'^'和'z'，而不是'^'确实是控制字符。

Currently you're actually detecting the characters '^' and 'z' it's not like '^' is really a control character.

实际上，您得到的异常提示应该如何处理。从 BufferedReader.readLine的文档中：

The exception you're getting is actually a hint as to how you should be handling this. From the docs for BufferedReader.readLine:

返回值：

包含以下内容的字符串行，不包括任何行终止符；如果已到达流的末尾，则返回null。

Returns:
A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached

readLine 返回 null 。

String line;
while((line = read.readLine()) != null)
{
    // Do something with line
}

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