How to read a file using Files.readAllBytes() in Java

The Files.readAllBytes() static method is a part of Java's non-blocking new I/O API (NIO). It can be used to read file contents into an array of bytes all at once.

Reading Text Files

Let us have an example to read a simple text file using Files.readAllBytes():

try {
    // read all bytes
    byte[] bytes = Files.readAllBytes(Paths.get("input.txt"));

    // convert bytes to string
    String content = new String(bytes);
    
    // print contents
    System.out.println(content);

} catch (IOException ex) {
    ex.printStackTrace();
}

The above program will produce the following output (depending on what input.txt includes on your computer):

This
is
an
example
file.

Reading Binary Files

To read a binary file and print the contents, we need to use the Arrays.toString() method to convert it to a string:

try {
    // read all bytes
    byte[] bytes = Files.readAllBytes(Paths.get("input.dat"));

    // convert bytes to string
    String content = Arrays.toString(bytes);

    // print contents
    System.out.println(content);

} catch (IOException ex) {
    ex.printStackTrace();
}

Here is the output of the above program (again depends on contents of input.dat):

[84, 104, 105, 115, 10, 105, 115, 10, 97, 110, 10, 101, 120, 97, 109, 112, 108, 101, 10, 102, 105, 108, 101, 46]

Further Reading

You may be interested in other Java I/O articles:

• Reading and Writing Files in Java
• How to Read and Write Text Files in Java
• How to Read and Write Binary Files in Java
• Reading and Writing Files using Java NIO API
• How to read a file line by line in Java

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