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Java in a Nutshell

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The java.io Package

24.57 java.io.Reader (JDK 1.1)

This abstract class is the superclass of all character input streams. It is an analog to InputStream, which is the superclass of all byte input streams. Reader defines the basic methods that all character output streams provide.

read() returns a single character or an array (or subarray) of characters, blocking if necessary. It returns -1 if the end of the stream has been reached. ready() returns true if there are characters available for reading. If ready() returns true, the next call to read() is guaranteed not to block. close() closes the character input stream. skip() skips a specified number of characters in the input stream. If markSupported() returns true, then mark() "marks" a position in the stream and, if necessary, creates a look-ahead buffer of the specified size. Future calls to reset() restore the stream to the marked position, if they occur within the specified look-ahead limit. Note that not all stream types support this mark-and-reset functionality.

To create a subclass of Reader, you need only implement the three-argument version of read() and close(). Most subclasses implement additional methods as well, however.

public abstract class Reader extends Object {
    // Protected Constructors
            protected Reader();
            protected Reader(Object lock);
    // Protected Instance Variables
            protected Object lock;
    // Public Instance Methods
            public abstract void close() throws IOException;
            public void mark(int readAheadLimit) throws IOException;
            public boolean markSupported();
            public int read() throws IOException;
            public int read(char[] cbuf) throws IOException;
            public abstract int read(char[] cbuf, int off, int len) throws IOException;
            public boolean ready() throws IOException;
            public void reset() throws IOException;
            public long skip(long n) throws IOException;

Extended By:

BufferedReader, CharArrayReader, FilterReader, InputStreamReader, PipedReader, StringReader

Passed To:

BufferedReader(), FilterReader(), LineNumberReader(), PushbackReader(), StreamTokenizer()

Type Of:


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