How can I read a large text file line by line using Java?

Question

I need to read a large text file of around 5-6 GB line by line using Java.

How can I do this quickly?

Answer 1

In Java 8, you could do:

try (Stream<String> lines = Files.lines (file, StandardCharsets.UTF_8))
{
    for (String line : (Iterable<String>) lines::iterator)
    {
        ;
    }
}

Some notes: The stream returned by Files.lines (unlike most streams) needs to be closed. For the reasons mentioned here I avoid using forEach(). The strange code (Iterable<String>) lines::iterator casts a Stream to an Iterable.

Answer 2

You need to use the readLine() method in class BufferedReader. Create a new object from that class and operate this method on him and save it to a string.

BufferReader Javadoc

Answer 3

You can also use Apache Commons IO:

File file = new File("/home/user/file.txt");
try {
    List<String> lines = FileUtils.readLines(file);
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}