Java BufferedReader无法读取文件内容

Question

I am currently trying to create a program to read and modify .test files (UTF-8, looks similar to an xml file) in order to avoid manually editing each one. I managed to get the program to successfully loop through the files in a folder, but my problem comes when trying to read the contents of the files. Currently my readFile function looks like this:

public static ArrayList<String> readFile(String fileName) {

    // This will reference one line at a time
    String line = null;

    try {
        // FileReader reads text files in the default encoding.
        File file = new File(fileName);

        BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file), "UTF8"));

        // Create arrayList to return
        ArrayList<String> fileContents = new ArrayList<String>();

        // Read first line
        line = reader.readLine();

        // Loop through file, and write each line to arrayList
        while(line != null) {
            fileContents.add(line);
            line = reader.readLine();
        }   

        // Close reader
        reader.close();

        // Return file contents
        return fileContents;
    }
    catch(FileNotFoundException ex) {
        System.out.println(
            "Unable to open file '" + fileName + "'");                
    }
    catch(IOException ex) {
        System.out.println("Error reading file '" + fileName + "'");                  
    }
    return null;
}

Where fileName is a string with the path to the file (ex: c:\\Tests\\test1.test).

I have tried using PrintReader, but that also did not work. The code is not throwing and exception, when I get to reading the first line (line = reader.readLine()) the reader return null, as if the file was empty. Am I using the reader incorrectly?

Any help or insight would be greatly appreciated. Thanks!

Answer 1

Getting null as a response is likely because your encoding is wrong. I notice you have "UTF8", shouldn't that be "UTF-8" or StandardCharsets.UTF_8.name()?

Answer 2

I managed to figure out the issue. On an earlier run the program must have erased the first file, so when the code was trying to read it, it was empty. This solution works, as well as @Sudhakar's solution as well.

Answer 3

You can try the below code to read the file content.

public static List<String> getFileContentAsList(String fileName) {
    File f = new File(fileName);
    try {
        return Files.readAllLines(f.toPath());
    } catch (IOException e) {
        e.printStackTrace();
    }

    return Collections.emptyList();
}