Exclude some files while reading multiple Files in Parallel using Java 8 Parallel Stream

Question

I am reading multiple files (1000 files of approx size 5mb) from folder. The code below is working fine to read, load and store the content of file.

public void readAllFiles(String path) {

    try (Stream<Path> paths = Files.walk(Paths.get(path)).collect(toList()).parallelStream()) {
        paths.forEach(filePath -> {

            if (filePath.toFile().exists()) {
                String fileName = filePath.getFileName().toString();
                try {
                        List<String> loadedFile = readContent(filePath);
                        storeFiles(fileName, filePath, loadedFile);
                } catch (Exception e) {
                    LOGGER.info("ERROR WHILE READING THE CONTENT OF FILE");
                    LOGGER.error(e.getMessage());
                }
            }
        });
    } catch (IOException e) {
        LOGGER.info("ERROR WHILE READING THE FILES IN PARALLEL");
        LOGGER.error(e.getMessage());
    }
}

My problem is while reading the files I want to exclude some files, like exclude the file reading if for example the condition satisfies (filename contains "ABC" && flag is true)

Thanks in advance for any suggestions.

Answer 1

Files.walk() returns Stream<Path> so you don't need to convert it to list. use the following code to use in parallel and filter it base on conditions.

try (Stream<Path> paths = Files.walk(Paths.get(path)).parallel()
    .filter(filePath->filePath.getFileName().toString().contains("ABC"))) {
        paths.forEach(filePath -> {
            //other staff...
        });
    } catch (IOException e) {

}

Answer 2

I would rewrite this using the filter function:

paths.filter(e -> e.toFile().exists())              //Make sure each file exists
     .map(path -> path.getFileName().toString())    //Map it to its fileName
     .filter(file -> !file.contains("someString"))  //Filter 
     .forEach(fileName -> {                         //Rest of logic
            try { 
                    List<String> loadedFile = readContent(filePath);
                    storeFiles(fileName, filePath, loadedFile);
            } catch (Exception e) {
                LOGGER.info("ERROR WHILE READING THE CONTENT OF FILE");
                LOGGER.error(e.getMessage());
            }            
    });

Which will map to a String representation of the before you do the forEach