Java : ScatteringByteChannel with Examples

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

Summary

A channel that can read bytes into a sequence of buffers.

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, 40, 50, 60, 70, 80, 90};
Files.write(path, bytes);

try (final ScatteringByteChannel channel = FileChannel.open(
        path, StandardOpenOption.READ)) {

    final ByteBuffer[] dsts = {
            ByteBuffer.allocate(2),
            ByteBuffer.allocate(3),
            ByteBuffer.allocate(4),
    };

    final var ret = channel.read(dsts);
    System.out.println(ret); // 9

    System.out.println("-- dsts --");
    for (final var dst : dsts) {
        if (dst.hasArray()) {
            System.out.println(Arrays.toString(dst.array()));
        }
    }

    // Result
    // ↓
    //-- dsts --
    //[10, 20]
    //[30, 40, 50]
    //[60, 70, 80, 90]
}

Methods

long read (ByteBuffer[] dsts)

Reads a sequence of bytes from this channel into the given buffers.

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, 40, 50, 60, 70, 80, 90};
Files.write(path, bytes);

try (final ScatteringByteChannel channel = FileChannel.open(
        path, StandardOpenOption.READ)) {

    final ByteBuffer[] dsts = {
            ByteBuffer.allocate(2),
            ByteBuffer.allocate(3),
            ByteBuffer.allocate(4),
    };

    final var ret = channel.read(dsts);
    System.out.println(ret); // 9

    System.out.println("-- dsts --");
    for (final var dst : dsts) {
        if (dst.hasArray()) {
            System.out.println(Arrays.toString(dst.array()));
        }
    }

    // Result
    // ↓
    //-- dsts --
    //[10, 20]
    //[30, 40, 50]
    //[60, 70, 80, 90]
}

long read (ByteBuffer[] dsts, int offset, int length)

Reads a sequence of bytes from this channel into a subsequence of the given buffers.

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, 40, 50, 60, 70, 80, 90};
Files.write(path, bytes);

try (final ScatteringByteChannel channel = FileChannel.open(
        path, StandardOpenOption.READ)) {

    final ByteBuffer[] dsts = {
            ByteBuffer.allocate(1),
            ByteBuffer.allocate(2),
            ByteBuffer.allocate(3),
            ByteBuffer.allocate(4),
            ByteBuffer.allocate(5),
    };

    final var ret = channel.read(dsts, 1, 3);
    System.out.println(ret); // 9

    System.out.println("-- dsts --");
    for (final var dst : dsts) {
        if (dst.hasArray()) {
            System.out.println(Arrays.toString(dst.array()));
        }
    }

    // Result
    // ↓
    //-- dsts --
    //[0]
    //[10, 20]
    //[30, 40, 50]
    //[60, 70, 80, 90]
    //[0, 0, 0, 0, 0]
}