Streams Cheat Sheet


Creating readers for different streams.

There are several ways to create Readers:

Reading from streams.

All readers allow you to read one character at a time with the read() method.
    int ch =;
The variable ch is set to a character value between 0 and 255, or -1 when there are no more characters left in the stream (i.e., at the end of a file).

To read whole lines at a time, use a BufferedReader:

    BufferedReader buffer = new BufferedReader(reader);
The reader variable is any reader made above. The following example shows how to read all lines in a file using a buffered reader:
    String s;
    BufferedReader buffer = new BufferedReader(new FileReader("filename"));
    s = buffer.readLine();
    while (s != null) {
        s = buffer.readLine();
The method readLine() returns null when the reader reaches the end of the stream.

Closing readers.

To close a reader, call the close() method:


Creating writers for different streams.

There are several ways to create Writers. We always want to create a PrintWriter for our writer so that we can write more than one character at a time:

Writing to streams.

You use a PrintWriter just as we have been using System.out all semester:
    writer.println("some text");
    writer.print("some text");
Unlike println, the print method does not start a new line after printing the text.

Closing writers.

Close writers just like readers: