在文件中查找单词并替换文件中新单词的方法(Java)

Question

It couldnt replace the new word and place it in a new file.

I want to create a method that take 4 parameters, one with oldfile, one with new file, one with old word and one with new word and they are all of type string.

I also want to make it so that he case of the first letter the oldWord should be maintained when writing to the in the newFile, eg if oldWord was “Hit” and newWord was “Cab” then if “Hit” is found in the oldFile then “Cab” should be written to the newFile.

Im not allowed to use advanced java stuff like hashkeys and all that. Hope that enough infomaton and thank you in advance.

My code couldnt print the new words into the new file instead it just prints 4 more lines of the new words in the old file.

//////

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class part2d {

    public static void main(String[] args)
        {
            modifyFile("test.txt","modify.txt", "Hit", "Cab");
            System.out.println("done");
        }

static void modifyFile(String oldfile, String newfile, String oldString, String newString)
{
    File fileToBeModified = new File("modify.txt");
    String oldContent = "";         
    BufferedReader reader = null;         
    FileWriter writer = null;
     
    try
    {
        reader = new BufferedReader(new FileReader(fileToBeModified));                     
        String line = reader.readLine();
         
        while (line != null) 
        {
            oldContent = oldContent + line + System.lineSeparator();                 
            line = reader.readLine();
        }
         
        String newContent = oldContent.replaceAll(oldString, newString);
         
        writer = new FileWriter(fileToBeModified,true);             
        writer.write(newContent);
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
    finally
    {
        try
        {                 
            reader.close();                 
            writer.close();
        } 
        catch (IOException e) 
        {
            e.printStackTrace();            
        }
    }

Answer 1

Both your reader and your writer are using the fileToBeModified variable. This variable is being set to modify.txt statically for both, so you're not actually reading and writing a new file, instead you're reading then appending the same file content again.

Think about what file you're creating using the BufferedReader/FileReader and the FileWriter, and consider how these are being set.