Package org.apache.commons.compress.compressors.bzip2

Class BZip2CompressorOutputStream

  • All Implemented Interfaces:
    Closeable, Flushable, AutoCloseable
    public class BZip2CompressorOutputStream
extends CompressorOutputStream
    An output stream that compresses into the BZip2 format into another stream.

    The compression requires large amounts of memory. Thus you should call the close() method as soon as possible, to force BZip2CompressorOutputStream to release the allocated memory.

    You can shrink the amount of allocated memory and maybe raise the compression speed by choosing a lower blocksize, which in turn may cause a lower compression ratio. You can avoid unnecessary memory allocation by avoiding using a blocksize which is bigger than the size of the input.

    You can compute the memory usage for compressing by the following formula: 

     <code>400k + (9 * blocksize)</code>.

    To get the memory required for decompression by BZip2CompressorInputStream use 

     <code>65k + (5 * blocksize)</code>.
    Memory usage by blocksize
    Memory usage by blocksize
    Blocksize Compression
    memory usage    		 Decompression
    memory usage
    100k 1300k 565k
    200k 2200k 1065k
    300k 3100k 1565k
    400k 4000k 2065k
    500k 4900k 2565k
    600k 5800k 3065k
    700k 6700k 3565k
    800k 7600k 4065k
    900k 8500k 4565k

    For decompression BZip2CompressorInputStream allocates less memory if the bzipped input is smaller than one block.

    Instances of this class are not threadsafe.

    TODO: Update to BZip2 1.0.1