CODEWITHSUNDEEP
javabufferedwriter
Melloorr
Melloorr

Reputation: 55

Writing to file in Java

First things first, I am a novice when it comes to Java. I have set myself a little project and I am currently stuck. I am trying to write to a file that already exists, but it just overwrites it. I am trying to replace the line that contains 'maxBooks'.

Here is the code than I am using:

FileWriter writeFile = new FileWriter(fileLocation);
            BufferedReader readLines = new BufferedReader(new FileReader(fileLocation));
            BufferedWriter writeLines = new BufferedWriter(writeFile);

            System.out.println("\n-----File Begin-----");

            while((finalLines = readLines.readLine()) != null){

                if(finalLines.contains("maxBooks")){
                    writeLines.newLine();
                    writeLines.write(finalLines);

                    System.out.println("This is the if statement");
                    System.out.println(finalLines);
                } else {
                    fileLines.add(new String(finalLines));
                    System.out.println("This is the else statement");
                    System.out.println(finalLines);
                }
            }

            System.out.println("------File End------");

Please bear in mind that I have left out the try and catch. Please let me know how I can edit the text file. Let me know if you need any more info

Thanks :)

EDIT

Sorry, I should clarify. I am just trying to edit 1 line that is in the test file, not the whole text file.

FINAL CODE:

FileWriter writeFile = new FileWriter(fileLocation + ".tmp", true);
            BufferedWriter writeLines = new BufferedWriter(writeFile);

            BufferedReader readLines = new BufferedReader(new FileReader(fileLocation));


            System.out.println("\n-----File Begin-----");

            while((finalLines = readLines.readLine()) != null){

                if(finalLines.contains("maxBooks")){
                    writeLines.write("maxBooks = " + maxBooks);
                    writeLines.newLine();

                    System.out.println("This is the if statement");
                    System.out.println(finalLines);
                } else {
                    fileLines.add(new String(finalLines));
                    System.out.println("This is the else statement");
                    writeLines.write(finalLines);
                    writeLines.newLine();
                }
            }

            System.out.println("------File End------");

            file2.renameTo(file);

            writeLines.close();

Upvotes: 1

Views: 318

Answers (2)

Muhammad Bekette
Muhammad Bekette

Reputation: 1434

you read and write on the same fileLocation you're supposed to give two differend locations;

goes something like this 

//define newLocation as string that contain path for new file to be written    
FileWriter writeFile = new FileWriter(newLocation);
                BufferedReader readLines = new BufferedReader(new FileReader(fileLocation));
                BufferedWriter writeLines = new BufferedWriter(writeFile);

Upvotes: 0

fge
fge

Reputation: 121840

You overwrite the file you try to read, which is bad practice. Write to a new file, then rename to the original file.

Upvotes: 3

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