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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.PushbackInputStream
java.io.FilterInputStream
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None
JDK 1.0 or later
The PushbackInputStream class represents a byte stream that allows data to be pushed back into the stream. In other words, after data has been read from a PushbackInputStream, it can be pushed back into the stream so that it can be reread. This functionality is useful for implementing things like parsers that need to read data and then return it to the input stream.
The PushbackInputStream has been enhanced as of JDK 1.1 to support a pushback buffer that is larger than one byte. Prior to JDK 1.1, the class supported only a one-byte buffer using the protected variable pushBack. As of 1.1, that variable has been replaced by the buf and pos variables.
public class java.io.PushbackInputStream extends java.io.FilterInputStream {
// Variables
protected byte[] buf; // New in 1.1
protected int pos; // New in 1.1
// Constructors
public PushbackInputStream(InputStream in);
public PushbackInputStream(InputStream in,
int size); // New in 1.1
// Instance Methods
public int available();
public boolean markSupported();
public int read();
public int read(byte[] b, int off, int len);
public void unread(int b);
public void unread(byte[] b); // New in 1.1
public void unread(byte[] b, int off, int len); // New in 1.1
}
New as of JDK 1.1
The buffer that holds data that has been pushed back.
New as of JDK 1.1
The position of pushed-back data in the buffer. When there is no pushed-back data, pos is buf.length. As data is pushed back, pos decreases. As pushed-back data is read, pos increases. When the pushback buffer is full, pos is 0.
The input stream to wrap.
This constructor creates a PushbackInputStream that reads from the given InputStream, using a pushback buffer with the default size of one byte.
New as of JDK 1.1
The input stream to wrap.
The size of the pushback buffer.
This constructor creates a PushbackInputStream that reads from the given InputStream, using a pushback buffer of the given size.
The number of bytes that can be read without blocking.
If any kind of I/O error occurs.
FilterInputStream.available()
This method returns the number of bytes that can be read without having to wait for more data to become available. This is b + u, where b is the number of bytes in the pushback buffer and u is the number of available bytes in the underlying stream.
The boolean value false.
FilterInputStream.markSupported()
This method returns false to indicate that this class does not support mark() and reset().
The next byte of data, or -1 if the end of the stream is encountered.
If any kind of I/O error occurs.
FilterInputStream.read()
This method reads a byte of data. If there is any data in the pushback buffer, the method returns the next byte in the pushback buffer. Otherwise, it calls the read() method of the underlying stream. The method blocks until the byte is read, the end of the stream is encountered, or an exception is thrown.
An array of bytes to be filled from the stream.
An offset into the byte array.
The number of bytes to read.
The actual number of bytes read, or -1 if the end of the stream is encountered immediately.
If any kind of I/O error occurs.
FilterInputStream.read(byte[], int, int)
This method copies bytes from the stream into the given array b, starting at index off and continuing for len bytes. If the array can be populated solely from the pushback buffer, the method returns immediately. Otherwise, the read(byte[], int, int) method of the underlying stream is called to make up the difference. The method blocks until some data is available.
The value to push back.
If the pushback buffer is full.
This method puts the given byte into the pushback buffer.
New as of JDK 1.1
An array of bytes to push back.
If the pushback buffer is full.
This method puts all of the bytes in the given array into the pushback buffer.
New as of JDK 1.1
An array of bytes to push back.
An offset into the array.
The number of bytes to push back.
If the pushback buffer is full.
This method puts len bytes from the given array, starting at offset off, into the pushback buffer.
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Method |
Inherited From |
Method |
Inherited From |
|---|---|---|---|
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clone() |
Object |
close() |
FilterInputStream |
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equals(Object) |
Object |
finalize() |
Object |
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getClass() |
Object |
hashCode() |
Object |
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mark(int) |
FilterInputStream |
notify() |
Object |
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notifyAll() |
Object |
read(byte[]) |
FilterInputStream |
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reset() |
FilterInputStream |
skip(long) |
FilterInputStream |
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toString() |
Object |
wait() |
Object |
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wait(long) |
Object |
wait(long, int) |
Object |
FilterInputStream, InputStream, IOException
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| PrintWriter |  |
PushbackReader |
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