1. Java IO Tutorial
2. Java IO Overview
3. Java IO: Files
4. Java IO: Streams
5. Java IO: Pipes
6. Java IO: Networking
7. Java IO: Byte & Char Arrays
8. Java System.in, System.out, and System.error
9. Java IO: Input Parsing
10. Java IO: Readers and Writers
11. Java IO: Concurrent IO
12. Java IO: Exception Handling
13. Java InputStream
14. Java OutputStream
15. Java FileInputStream
16. Java FileOutputStream
17. Java RandomAccessFile
18. Java File
19. Java IO: PipedInputStream
20. Java IO: PipedOutputStream
21. Java ByteArrayInputStream
22. Java ByteArrayOutputStream
23. Java IO: FilterInputStream
24. Java IO: FilterOutputStream
25. Java BufferedInputStream
26. Java BufferedOutputStream
27. Java PushbackInputStream
28. Java IO: SequenceInputStream
29. Java DataInputStream
30. Java IO: DataOutputStream
31. Java IO: PrintStream
32. Java IO: ObjectInputStream
33. Java IO: ObjectOutputStream
34. Java IO: Serializable
35. Java Reader
36. Java Writer
37. Java InputStreamReader
38. Java OutputStreamWriter
39. Java FileReader
40. Java FileWriter
41. Java IO: PipedReader
42. Java IO: PipedWriter
43. Java IO: CharArrayReader
44. Java IO: CharArrayWriter
45. Java BufferedReader
46. Java BufferedWriter
47. Java IO: FilterReader
48. Java IO: FilterWriter
49. Java PushbackReader
50. Java IO: LineNumberReader
51. Java StreamTokenizer
52. Java IO: PrintWriter
53. Java IO: StringReader
54. Java IO: StringWriter

• PipedReader Example
• read()
• Java IO Pipes
• Closing a PipedReader

The Java PipedReader class (java.io.PipedReader) makes it possible to read the contents of a pipe as a stream of characters. As such it works very much like a PipedInputStream except the PipedInputStream is byte based, not character based. The PipedReader is intended to read text, in other words.

A Java PipedReader must be connected to a PipedWriter. Often, the PipedReader and PipedWriter are used by different threads. Only one PipedReader can be connected to the same PipedWriter.

PipedReader Example

Here is a simple Java PipedReader example:

PipedWriter pipedWriter = new PipedWriter();
PipedReader pipedReader = new PipedReader(pipedWriter);

int data = pipedReader.read();
while(data != -1) {
  //do something with data...
  doSomethingWithData(data);

  data = pipedReader.read();
}
pipedReader.close();

Note: The proper exception handling has been skipped here for the sake of clarity. To learn more about correct exception handling, go to Java IO Exception Handling.

read()

The read() method of a Java PipedReader returns an int which contains the char value of the character read. If the read() method returns -1, there is no more data to read in the PipedReader, and it can be closed. That is, -1 as int value, not -1 as byte value. There is a difference here!

Java IO Pipes

As you can see in the example above, a PipedReader needs to be connected to a PipedWriter. When these two character streams are connected they form a pipe. To learn more about Java IO pipes, go to Java IO: Pipes.

Closing a PipedReader

When you are finished reading characters from a Java PipedReader you should remember to close it. Closing a PipedReader is done by calling its close() method.

Closing a PipedReader does not close the PipedWriter it is connected to. But - even if the PipedReader is closed you cannot connect a new PipedReader to the PipedWriter.

Here is how closing a Java PipedReader looks:

pipedReader.close();

You can also use the try-with-resources construct introduced in Java 7. Here is how to use and close a PipedReader looks with the try-with-resources construct:

try(PipedReader pipedReader =
    new PipedReader(pipedWriter)){

    int data = pipedReader.read();
    while(data != -) {
        System.out.print((char) data));
        data = pipedReader.read();
    }
}

Notice how there is no longer any explicit close() method call to the PipedReader instance. The try-with-resources construct takes care of that.