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Java Examples: PipedWriter and PipedReader

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Here are Java examples of PipedWriter and PipedReader.

Here are Java examples of PipedWriter and PipedReader.

1. Introduction to PipedReader and PipedWriter

"PipedReader" class is used to read the text stream of data, and "PipedWriter" is used to write the text stream of data. In Java, these PipedReaders and PipedWriters are used in pairs. Like the producer and consumer situation, the writer writes the data at one end of the pipe, and the reader reads it at the other end. Usually, the reader and writer operate asynchronously with the help of threads. In our example, we are not going to use threads for simplicity.

For example, let us say we are writing an application that receives SMS (Short Message Text) from different mobile numbers with a request code. The application searches the requested data in the in-house database and sends back the information to the requested mobile number. In this case, two piped text streams can be used. One pipe is for receiving the SMS, and the other one is for sending the SMS.

The receiving and sending pipe can be constructed with PipedReader and PipedWriter. Let us consider only the receiving pipe. Here, the writer reads the incoming message from GSM Modem (hardware attached to the system) and writes to one end of the pipe, and the reader receives (reads) the SMS message at the other end. The same goes while sending the message by switching the PipedReader and PipedWriter ends.

The data flow is in a single direction from the writer-end of the pipe to the reader-end of the pipe. OK, let us start with an example. Here, we will write a stream of text using PipedWriter and read the data written from the other end using PipedReader.

2. Create PipedReader and PipedWriter

First the required classes are imported from the "Java.io Package". The code for that is below:

//Sample 01: Package inclusion
import java.io.PipedReader;
import java.io.PipedWriter;
import java.io.IOException;

Next, we are creating PipedReader and PiperWriter objects and storing the references in ReaderEnd and WriterEnd, respectively. The PipedWriter is used to write the text content, and PipedReader is used to read the text content from the pipe.

Once the objects are created, they are connected together to form the pipe by making a call to the method “connect()”. Note that both PipedReader and PipedWriter support the connect method. When we call the “connect()” method on the PipedWriter object, we have to pass PipedReader as a parameter. In our example, we are calling the connect on PipedReader object ReaderEnd. After the method call, we will have the PipedReader and PipedWriter form a pipe connection with Writer at one end and Reader at another end. Below is the code:

//Sample 02: Create Piped Reader and Piped Writer
PipedReader ReaderEnd = new PipedReader();
PipedWriter WriterEnd = new PipedWriter();

//Sample 03: Connect the PipedReader and PipedWriter
ReaderEnd.connect(WriterEnd);

3. PipedWriter Writes and PiperReader Reads

Once we have Pipe is Connected with the Reader and Writer, we write the Stream Of Text to the Pipe from one end by making use of WriterEnd instance. We are writing all the ASCII characters ranging from Uppercase ‘A’ to Lowercase ‘z’ to the Pipe by calling the “write()” method. Below is the code that writes text stream to the Pipe:

//Sample 04: Write the Character Stream at one end
for (int i = (int)('A'); i < ((int) ('z')) + 1; i++)
    WriterEnd.write((char) i );

The stream text written by the PipedWriter and at one end of the Pipe is read by the PipedReader on the other end by making use of the “read()” method. Note that the PipedReader object ReaderEnd reads the object in the same order in which it is written to the Pipe. For example, the writer wrote the letter ‘A’ first to the Pipe, and the Reader reads that first. Below is the code:

//Sample 05: Read the Character from the Other End
for (int i = (int)('A'); i < ((int) ('z')) + 1; i++ ) {
    int chr = ReaderEnd.read();
    System.out.print((char) chr);
}

Now have a look at the depiction below:

Reading and Writing TextStream through PipedWriter and PipedReader

Reading and Writing TextStream through PipedWriter and PipedReader

Below is the complete code example and its output:

//Sample 01: Package inclusion
import java.io.PipedReader;
import java.io.PipedWriter;
import java.io.IOException;

public class Main {
    public static void main(String[] args) {
        try
        {
            //Sample 02: Create Piped Reader and Piped Writer
            PipedReader ReaderEnd = new PipedReader();
            PipedWriter WriterEnd = new PipedWriter();

            //Sample 03: Connect the PipedReader and PipedWriter
            ReaderEnd.connect(WriterEnd);

        //Sample 04: Write the Character Stream at one end
        for (int i = (int)('A'); i < ((int) ('z')) + 1; i++)
            WriterEnd.write((char) i );

        //Sample 05: Read the Character from the Other End
        for (int i = (int)('A'); i < ((int) ('z')) + 1; i++ ) {
            int chr = ReaderEnd.read();
            System.out.print((char) chr);
        }

        } catch (IOException Ex)
        {
            System.out.println(Ex.getMessage());
        }
    }
}

The output of the above code is thus:

ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

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