java - 读取、扫描、修改文本文件并将修改后的文本放入新文件中

Question

我尝试读取文本文件并尝试修改它。我从 StackOverflow 得到了很多讨论，以下是内容:

NO 1025 0

NO 1025 1

OP 1026 0

EndRow

我想要的修改后的文本文件:

NO 0

AND 1

OP 0

EndRow

我阅读了一些有关它的讨论主题，然后得出的结论是我必须使用 .hasNextLine 方法来检查每一行。代码如下:

import java.io.*;
import java.util.Scanner;

public class MainConvert {

/**
 * @nahdiya
 */
public static void main(String[] args) {
    try {
        File readNet = new File("testttt.net");
        FileReader readFileNet = new FileReader(readNet);
        BufferedReader reader = new BufferedReader(readFileNet);
        Scanner scan = new Scanner("testttt.net");
        PrintWriter fileConvert = new PrintWriter("convertNet.txt");
        while (scan.hasNextLine()) {
            String check = scan.next();
            String checkLine = scan.nextLine();
            if (checkLine.contains("NO 1025")) {
                if(checkLine.contains("NO 1025")) {
                    fileConvert.println("AND "+check );
                } else if (checkLine.contains("OP 1026")) {
                    fileConvert.println("OP"+check);
                } else {
                    fileConvert.println(checkLine);}
                }
            }
        }
        reader.close();
        fileConvert.close();
    } catch(Exception ex) {
        ex.printStackTrace();
    }
}

当我尝试运行该类时，输出消息如下所示:

java.util.NoSuchElementException: No line found
    at java.util.Scanner.nextLine(Unknown Source)
    at fileConvertSave.MainConvert.main(MainConvert.java:21)

问题是:

PrintWriter fileConvert = new PrintWriter("convertNet.txt");

这条线有什么问题吗？我只想修改 testttt.net 文件。 fileConvert 必须创建为新文件。这是什么问题？

Answer 1

已编辑:请参阅底部的完整解决方案:

产生错误消息的原始问题是扫描程序尝试在不存在的行上执行 nextLine()，原因是:

String check = scan.next(); 
String checkLine = scan.nextLine(); 

当你打电话时:

while( scan.hasNextLine() ) 

还有下一行可用。然后你调用:

scan.next();

此时可能不再有“下一行”可用。然后你调用:

scan.nextLine() 

然后繁荣起来。

删除线

String check = scan.next();

应该可以工作。

编辑:

这是问题所有其他部分的解决方案...它基本上是对您所拥有的内容的完全重写，因此请阅读所有代码，了解它的作用并尝试了解这一切!如果有疑问，请在提问之前先阅读文档。

BufferedReader reader = null;
PrintWriter writer = null;

try {                                    
    reader = new BufferedReader(new FileReader("testttt.txt"));                       
    writer = new PrintWriter("convertNet.txt");            

    // setup the pattern that we want to find and replace in the input:
    // NB> this is a regex (or regular expression)
    // it means, find [space] then either 1025 or 1026 then [space]
    String patternToMatch = " (1025|1026) ";

    String inputLine = null;

    // while there are lines to read, read them one at a time:
    while ((inputLine = reader.readLine()) != null) {

        // create the outputLine which is the input line with our pattern
        // " 1025 " or " 1026 "  replaced by just a single space:
        String outputLine = inputLine.replaceFirst(patternToMatch, " ");

        // log the transformation for debugging purposes:                               
        System.out.println(inputLine + " -> " + outputLine);

        // write the outputLine to the output file:
        writer.println(outputLine);
    }
}  
catch (FileNotFoundException ex) {
    System.out.println("file was not found: " + ex);        
} 
catch (IOException ex ) {
    System.out.println("io error: " + ex);
}
finally {
    try {
        if( reader != null ) reader.close();
        if ( writer != null ) writer.close();
    } catch (IOException ex) {
        System.out.println("error closing file " + ex);
    }
}  

请注意，即使出现异常，finally block 也能很好地进行清理。还有一种更新的方法可以做到这一点，可以使代码更短一些，称为 try with resources:

http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html