Question

Im making a recursive file checking, the problem is i cant have counter inside the method itself, so that i declared it outside. But the problem is, this isnt thread safe.

private int countFiles = 0;
private int getTotalFiles(String path) {

    File file = new File(path);
    File listFile[] = file.listFiles();

    for (File f : listFile) {
        if (f.isFile()) {
            countFiles++;
        }
        if (f.isDirectory()) {
            getTotalFiles(f.getAbsolutePath());
        }
    }

    return countFiles;
}

Class variable countFiles is not thread safe. How to make this thread safe ?

Answer 1

You don’t need a field, just add the result of the recursive call to countFiles.

private int getTotalFiles(String path) {
    //...
    if (f.isFile()) {
        countFiles++;
    }
    if (f.isDirectory()) {
        countFiles += getTotalFiles(path);
    }
}