java.io
Class FilterInputStream

java.lang.Object
  java.io.InputStream
      java.io.FilterInputStream

Direct Known Subclasses:

BufferedInputStream

public class FilterInputStream
extends InputStream

This is the common superclass of all standard classes that filter input. It acts as a layer on top of an underlying InputStream and simply redirects calls made to it to the subordinate InputStream instead. Subclasses of this class perform additional filtering functions in addition to simply redirecting the call.

This class is not abstract. However, since it only redirects calls to a subordinate InputStream without adding any functionality on top of it, this class should not be used directly. Instead, various subclasses of this class should be used. This is enforced with a protected constructor. Do not try to hack around it.

When creating a subclass of FilterInputStream, override the appropriate methods to implement the desired filtering. However, note that the read(byte[]) method does not need to be overridden as this class redirects calls to that method to read(byte[], int, int) instead of to the subordinate InputStream read(byte[]) method.

Field Summary

protected InputStream

in This is the subordinate InputStream to which method calls are redirected

Constructor Summary

protected

FilterInputStream(InputStream in) Create a FilterInputStream with the specified subordinate InputStream.

Method Summary

int	available() Calls the in.available() method.
void	close() This method closes the input stream by closing the input stream that this object is filtering.
void	mark(int readlimit) Calls the in.mark(int) method.
boolean	markSupported() Calls the in.markSupported() method.
int	read() Calls the in.read() method
int	read(byte[] buf) Calls the read(byte[], int, int) overloaded method.
int	read(byte[] buf, int offset, int len) Calls the in.read(byte[], int, int) method.
void	reset() Calls the in.reset() method.
long	skip(long numBytes) Calls the in.skip(long) method

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

in

protected InputStream in

This is the subordinate InputStream to which method calls are redirected

Constructor Detail

FilterInputStream

protected FilterInputStream(InputStream in)

Create a FilterInputStream with the specified subordinate InputStream.

Parameters:

in - The subordinate InputStream

Method Detail

mark

public void mark(int readlimit)

Calls the in.mark(int) method.

Overrides:

mark in class InputStream

Parameters:

readlimit - The parameter passed to in.mark(int)

markSupported

public boolean markSupported()

Calls the in.markSupported() method.

Overrides:

markSupported in class InputStream

Returns:

true if mark/reset is supported, false otherwise

reset

public void reset()
           throws IOException

Calls the in.reset() method.

Overrides:

reset in class InputStream

Throws:

IOException - If an error occurs

available

public int available()
              throws IOException

Calls the in.available() method.

Overrides:

available in class InputStream

Returns:

The value returned from in.available()

Throws:

IOException - If an error occurs

skip

public long skip(long numBytes)
          throws IOException

Calls the in.skip(long) method

Overrides:

skip in class InputStream

Parameters:

numBytes - The requested number of bytes to skip.

Returns:

The value returned from in.skip(long)

Throws:

IOException - If an error occurs

read

public int read()
         throws IOException

Calls the in.read() method

Specified by:

read in class InputStream

Returns:

The value returned from in.read()

Throws:

IOException - If an error occurs

read

public int read(byte[] buf)
         throws IOException

Calls the read(byte[], int, int) overloaded method. Note that this method does not redirect its call directly to a corresponding method in in. This allows subclasses to override only the three argument version of read.

Overrides:

read in class InputStream

Parameters:

buf - The buffer to read bytes into

Returns:

The value retured from in.read(byte[], int, int)

Throws:

IOException - If an error occurs

read

public int read(byte[] buf,
                int offset,
                int len)
         throws IOException

Calls the in.read(byte[], int, int) method.

Overrides:

read in class InputStream

Parameters:

buf - The buffer to read bytes into

offset - The index into the buffer to start storing bytes

len - The maximum number of bytes to read.

Returns:

The value retured from in.read(byte[], int, int)

Throws:

IOException - If an error occurs

close

public void close()
           throws IOException

This method closes the input stream by closing the input stream that this object is filtering. Future attempts to access this stream may throw an exception.

Overrides:

close in class InputStream

Throws:

IOException - If an error occurs