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Chapter 11 The java.io Package |
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Chapter 11 The java.io Package |
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java.io.FilterReader
java.io.Reader
java.io.PushbackReader
None
New as of JDK 1.1
The FilterReader class is the superclass of all of the reader classes that filter input. A subclass of FilterReader works by wrapping an existing reader, called the underlying reader, and providing additional functionality. The methods of FilterReader simply override the methods of Reader with versions that call the corresponding methods of the underlying reader.
FilterReader cannot be instantiated directly; it must be subclassed. An instance of a subclass of FilterReader is constructed with another Reader object. The methods of a subclass of FilterReader should override some methods in order to extend their behavior or provide some sort of filtering.
FilterReader is like FilterInputStream, except that it deals with a character stream instead of a byte stream.
public abstract class java.io.FilterReader extends java.io.Reader {
// Variables
protected Reader in;
// Constructors
protected FilterReader(Reader in);
// Instance Methods
public void close();
public void mark(int readAheadLimit);
public boolean markSupported();
public int read();
public int read(char[] cbuf, int off, int len);
public boolean ready();
public void reset();
public long skip(long n);
}
The underlying reader that this FilterReader wraps or filters.
The input reader to filter.
This constructor creates a FilterReader that gets data from in.
If any kind of I/O error occurs.
Reader.close()
This method calls the close() method of the underlying reader, which releases any system resources associated with this object.
The maximum number of characters that can be read before the saved position becomes invalid.
If any kind of I/O error occurs.
Reader.mark()
This method calls the mark() method of the underlying reader. If the underlying reader supports mark() and reset(), this method causes the FilterReader to remember its current position. A subsequent call to reset() causes the object to return to that saved position, and thus re-read a portion of the input.
true if this reader supports mark() and reset(); false otherwise.
Reader.markSupported()
This method calls the markSupported() method of the underlying reader and returns the result.
The next character of data or -1 if the end of the stream is encountered.
If any kind of I/O error occurs.
Reader.read()
This method calls the read() method of the underlying reader and returns the result. The method blocks until data is available, the end of the stream is detected, or an exception is thrown.
An array of characters to be filled from the stream.
An offset into the array.
The number of characters to read.
The actual number of characters read or -1 if the end of the stream is encountered immediately.
If any kind of I/O error occurs.
Reader.read(char[], int, int)
This method reads up to len characters of input into the given array starting at index off. It does this by calling the read(char[], int, int) method of the underlying reader and returning the result. The method blocks until some data is available.
A boolean value that indicates whether the reader is ready to be read.
If the stream is closed.
Reader.ready()
This method calls the ready() method of the underlying reader and returns the result. If the underlying stream is ready, this method returns true. The underlying stream is ready if the next read() is guaranteed not to block.
If the stream is closed, mark() has not been called, or the saved position has been invalidated.
Reader.reset()
This method calls the reset() method of the underlying reader. If the underlying reader supports mark() and reset(), this method sets the position of the FilteredReader to a position that was saved by a previous call to mark(). Subsequent characters read from this FilteredReader will begin from the saved position and continue normally.
The number of characters to skip.
The actual number of characters skipped.
If any kind of I/O error occurs.
Reader.skip()
This method skips n characters of input. It calls the skip() method of the underlying reader.
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Method |
Inherited From |
Method |
Inherited From |
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clone() |
Object |
equals(Object) |
Object |
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finalize() |
Object |
getClass() |
Object |
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hashCode() |
Object |
notify() |
Object |
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notifyAll() |
Object |
toString() |
Object |
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wait() |
Object |
wait(long) |
Object |
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wait(long, int) |
Object |
FilterInputStream, IOException, PushbackReader, Reader
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| FilterOutputStream |  |
FilterWriter |
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