Java PipedInputStream & PipedOutputStream

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PipedInputStream and PipedOutputStream in Java create a pipe for communication between two threads.

 

A PipedInputStream allows for reading any data that has been written to a PipedOutputStream.

 

notepad

Used for inter-thread communication in producer-consumer scenarios.

Syntax

Create Pipe

PipedOutputStream pos = new PipedOutputStream();
PipedInputStream pis = new PipedInputStream(pos); // Connected

 

Or connect later:

 PipedOutputStream pos = new PipedOutputStream();
PipedInputStream pis = new PipedInputStream();
pos.connect(pis);

Example

import java.io.*;

public class PipeExample {
    public static void main(String[] args) throws IOException {
        final PipedInputStream pis = new PipedInputStream();
        final PipedOutputStream pos = new PipedOutputStream(pis);

        Thread writer = new Thread(() -> {
            try {
                String message = "Hello from writer thread!";
                pos.write(message.getBytes());
                pos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        });

        Thread reader = new Thread(() -> {
            try {
                int data;
                while ((data = pis.read()) != -1) {
                    System.out.print((char) data);
                }
                pis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        });

        writer.start();
        reader.start();
    }
}

Output

Hello from writer thread!

PipedOutputStream

Method Description
write(int b) Writes a byte to the stream
write(byte[] b) Writes an array of bytes
close() Closes the stream

PipedInputStream

Method Description
read() Reads one byte of data
read(byte[] b) Reads bytes into the array
available() Number of bytes available to read
close() Closes the stream

Key Points

  • Inter-thread communication requires the use of pipes between distinct threads.
  • Users need to connect both ends of the pipe before they can begin operating with it.
  • Always handle exceptions and close streams.
  • This communication method does not support thread-safe operations involving multiple writers or readers.
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