从文件中删除数据时，临时文件不会重命名回原始文件

Question

I am trying to remove a line based on user input. myFile.txt looks like:

Matt
Brian
John

However when I enter "Brian" (to remove this line), It is deleted on the temp file (myTempFile.txt), but not renamed back to the original file (myFile). Why is this? Thanks

import java.io.BufferedReader;
    import java.io.BufferedWriter;
    import java.io.File;
    import java.io.FileNotFoundException;
    import java.io.FileReader;
    import java.io.FileWriter;
    import java.io.IOException;
    import java.util.Scanner;

    public class testcode {

        public static void main(String[] args) throws IOException   {
            File inputFile = new File("myFile.txt");
            File tempFile = new File("myTempFile.txt");
            Scanner myScan = new Scanner(System.in);

            BufferedReader reader = new BufferedReader(new FileReader(inputFile));
            BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));

            System.out.print("Please enter student first name: ");
            String lineToRemove = myScan.nextLine();
            String currentLine;

            while((currentLine = reader.readLine()) != null)
            {
                String trimmedLine = currentLine.trim();
                if(!trimmedLine.contains(lineToRemove)) {
                    writer.write(trimmedLine);
                    writer.newLine();
                }
                tempFile.renameTo(inputFile);   
            }
            writer.close();
            reader.close();
            myScan.close();

        }
    }

Answer 1

Your original file is open that's why it's not working.

I suggest to do the renameTo(...) after the while and put a reader.close(); before it. It makes no sense to rename it at each readLine() of your original file. Do the processing, then rename the temporary file.

Like:

while((currentLine = reader.readLine()) != null)
    {
        String trimmedLine = currentLine.trim();
        if(!trimmedLine.contains(lineToRemove)) {
            writer.write(trimmedLine);
            writer.newLine();
        }

    }            
    reader.close();
    writer.close();
    inputFile.delete(); //Added to my original post.
    tempFile.renameTo(inputFile);  

See as example: http://www.tutorialspoint.com/java/io/file_renameto.htm

After some research, I saw this: http://www.coderanch.com/t/595269/java-io/java/doesn-File-renameTo-work . If the file does exist, the renaming will not work. Try to Delete the inputFile before renaming.