Java : Flushable with Examples

Flushable (Java SE 21 & JDK 21) with Examples.
You will find code examples on most Flushable methods.


Summary

A Flushable is a destination of data that can be flushed. The flush method is invoked to write any buffered output to the underlying stream.

Class diagram

final var out = new ByteArrayOutputStream();
try (final var os = new BufferedOutputStream(out)) {

    final Flushable flushable = os;

    os.write(10);
    System.out.println(Arrays.toString(out.toByteArray())); // []

    flushable.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10]

    os.write(20);
    System.out.println(Arrays.toString(out.toByteArray())); // [10]

    flushable.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20]

    os.write(30);
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20]

    flushable.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30]
}

Methods

void flush ()

Flushes this stream by writing any buffered output to the underlying stream.

final var out = new ByteArrayOutputStream();
try (final var os = new BufferedOutputStream(out)) {

    final Flushable flushable = os;

    os.write(10);
    System.out.println(Arrays.toString(out.toByteArray())); // []

    flushable.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10]

    os.write(20);
    System.out.println(Arrays.toString(out.toByteArray())); // [10]

    flushable.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20]

    os.write(30);
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20]

    flushable.flush();
    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30]
}

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