Java.io.PipedInputStream class in Java

Pipes in IO provides a link between two threads running in JVM at the same time. So, Pipes are used both as source or destination.

• PipedInputStream is also piped with PipedOutputStream. So, data can be written using PipedOutputStream and can be written using PipedInputStream.But, using both threads at the same time will create a deadlock for the threads.
• A pipe is said to be broken if a thread that was providing data bytes to the connected piped output stream is no longer alive.

Declaration:

public class PipedInputStream
  extends InputStream

Constructor :

• PipedInputStream() : creates a PipedInputStream, that it is not connected.
• PipedInputStream(int pSize) : creates a PipedInputStream, that it is not connected with specified pipe size.
• PipedInputStream(PipedOutputStream outStream) : creates a PipedInputStream, that it is connected to PipedOutputStream – ‘outStream’.
• PipedInputStream(PipedOutputStream outStream, int pSize) : creates a Piped Input Stream that is connected to Piped Output Stream with the specified pipe size.

Methods:

• int read(): Reads the next byte of data from this piped input stream.The value byte is returned as an int in the range 0 to 255. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

  // Java program illustrating the working of read() method
  import java.io.*;
  public class NewClass
  {
      public static void main(String[] args) throws IOException
      {
          PipedInputStream geek_input = new PipedInputStream();
          PipedOutputStream geek_output = new PipedOutputStream();
          try
          {
              // Use of connect() : connecting geek_input with geek_output
              geek_input.connect(geek_output);
  
              // Use of read() method :
              geek_output.write(71);
              System.out.println("using read() : " + (char)geek_input.read());
              geek_output.write(69);
              System.out.println("using read() : " + (char)geek_input.read());
              geek_output.write(75);
              System.out.println("using read() : " + (char)geek_input.read());
  
          }
          catch (IOException except)
          {
              except.printStackTrace();
          }
      }
  }

  Output :

  using read() : G
  using read() : E
  using read() : K

• read(byte[] buffer, int offset, int maxlen) : java.io.PipedInputStream.read(byte[] buffer, int offset, int maxlen) reads upto maxlen bytes of the data from Piped Input Stream to the array of buffers. The method blocks if end of Stream is reached or exception is thrown.
  Syntax :

  public int read(byte[] buffer, int offset, int maxlen)
  Parameters : 
  buffer : the destination buffer into which the data is to be read
  offset : starting in the destination array - 'buffer'.
  maxlen : maximum length of array to be read
  Return :                                               
  next 'maxlen' bytes of the data as an integer value 
  return -1 is end of stream is reached
  Exception :
  -> IOException : if in case IO error occurs.
  -> NullPointerException : if buffer is null.
  -> IndexOutOfBoundsException : if offset is -ve or 
                                  maxlen is -ve or maxlen > buffer.length - offset.
  

• receive(int byte) : java.io.PipedInputStream.receive(int byte) receives byte of the data. If no input is available, then the method blocks.
  Syntax :

  protected void receive(int byte)
  Parameters : 
  byte : the bytes of the data received
  Return :                                               
  void
  Exception :
  -> IOException : if in case IO error occurs or pipe is broken.

• close() : java.io.PipedInputStream.close() closes the Piped Input Stream and releases the allocated resources.
  Syntax :

  public void close()
  Parameters : 
  --------------
  Return :                                               
  void
  Exception :
  -> IOException : if in case IO error occurs.

• connect(PipedOutputStream source) : java.io.PipedInputStream.connect(PipedOutputStream source) connects the Piped Input Stream to the ‘source’ Piped Output Stream and in case ‘source’ is pipes with some other stream, IO exception is thrown
  Syntax :

  public void connect(PipedOutputStream source)
  Parameters : 
  source : the Piped Output Stream to be connected to
  Return :                                               
  void
  Exception :
  -> IOException : if in case IO error occurs.

• available() : java.io.PipedInputStream.available() returns no. of bytes that can be read from Input Stream without actually being blocked.
  Syntax :

  public int available()
  Parameters : 
  -------------
  Return :                                               
  no. of bytes that can be read from Input Stream without actually being blocked.
  0, if the stream is already closed but by invoking close() method
  Exception :
  -> IOException : if in case IO error occurs.

Java program explaining the working of PipedInputStream class methods :

// Java program illustrating the working of PipedInputStream
// connect(), read(byte[] buffer, int offset, int maxlen),
// close(), available()

import java.io.*;
public class NewClass
{
    public static void main(String[] args) throws IOException
    {
        PipedInputStream geek_input = new PipedInputStream();
        PipedOutputStream geek_output = new PipedOutputStream();
        try
        {
            // Use of connect() : connecting geek_input with geek_output
            geek_input.connect(geek_output);

            geek_output.write(71);
            geek_output.write(69);
            geek_output.write(69);
            geek_output.write(75);
            geek_output.write(83);

            // Use of available() :
            System.out.println("Use of available() : " + geek_input.available());

            // Use of read(byte[] buffer, int offset, int maxlen) :
            byte[] buffer = new byte[5];
            // destination 'buffer'
            geek_input.read(buffer, 0, 5);

            String str = new String(buffer);
            System.out.println("Using read(buffer, offset, maxlen) : " + str);

            // USe of close() method :
            System.out.println("Closing the stream");
            geek_input.close();

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

Output:

Use of available() : 5
Using read(buffer, offset, maxlen) : GEEKS
Closing the stream

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