Java IO.pdf - Nguyen Dang Binh

Java I/O
The first method fills the specified output array with the bytes of compressed data. The
second fills the specified subarray of output beginning at offset and continuing for length
bytes with the compressed data. Both methods return the actual number of compressed bytes
written into the array. You do not know in advance how many compressed bytes will actually
be written into output, because you do not know how well the data will compress. You
always have to check the return value. If deflate() returns 0, you should check
needsInput() to see if you need to call setInput() again to provide more uncompressed
input data:
public boolean needsInput()
When more data is needed, the needsInput() method returns true. At this point you should
invoke setInput() again to feed in more uncompressed input data, call deflate(), and
repeat the process until deflate() returns and there is no more input data to be compressed.
9.1.1.7 Finish the deflation
Finally, when the input data is exhausted, invoke finish() to indicate that no more data is
forthcoming and the deflater should finish with the data it already has in its buffer:
public synchronized void finish()
The finished() method returns true when the end of the compressed output has been
reached; that is, when all data stored in the input buffer has been deflated:
public synchronized boolean finished()
After calling finish(), you invoke deflate() repeatedly until finished() returns true.
This flushes out any data that remains in the input buffer.
9.1.1.8 Reset the deflater and start over
This completes the sequence of method invocations required to compress data. If you'd like to
use the same strategy, compression level, and other settings to compress more data with the
same Deflater, call its reset() method:
public native synchronized void reset()
Otherwise, call end() to throw away any unprocessed input and free the resources used by the
native code:
public native synchronized void end()
The finalize() method calls end() before the deflater is garbage-collected, if you forget:
protected void finalize()
9.1.1.9 An example
Example 9.1 is a simple program that deflates files named on the command line. First
a Deflater object, def, is created with the default strategy, method, and compression level.
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