Java : ByteChannel with Examples

ByteChannel (Java SE 20 & JDK 20) API Examples.
You will find code examples on most ByteChannel methods.

Summary

A channel that can read and write bytes. This interface simply unifies ReadableByteChannel and WritableByteChannel; it does not specify any new operations.

Class diagram

final var path = Path.of("R:", "java-work", "test.data");
System.out.println(path); // R:\java-work\test.data

final byte[] bytes = {10, 20, 30};
Files.write(path, bytes);

try (final ByteChannel channel = Files.newByteChannel(path,
        StandardOpenOption.CREATE, StandardOpenOption.WRITE, StandardOpenOption.READ)) {

    final var array = new byte[5];

    final var buffer = ByteBuffer.wrap(array);
    System.out.println(buffer); // java.nio.HeapByteBuffer[pos=0 lim=5 cap=5]

    System.out.println(buffer.position()); // 0
    System.out.println(Arrays.toString(array)); // [0, 0, 0, 0, 0]

    final var ret1 = channel.read(buffer);
    System.out.println(ret1); // 3

    System.out.println(buffer.position()); // 3
    System.out.println(Arrays.toString(array)); // [10, 20, 30, 0, 0]

    buffer.put(3, (byte) 40);
    buffer.put(4, (byte) 50);

    System.out.println(buffer.position()); // 3
    System.out.println(Arrays.toString(array)); // [10, 20, 30, 40, 50]

    final var ret2 = channel.write(buffer);
    System.out.println(ret2); // 2

    System.out.println(buffer.position()); // 5
}

final var ret = Files.readAllBytes(path);
System.out.println(Arrays.toString(ret)); // [10, 20, 30, 40, 50]