Class Deflater
 Unless otherwise noted, passing a null argument to a method
 in this class will cause a NullPointerException to be
 thrown.
 
 This class deflates sequences of bytes into ZLIB compressed data format.
 The input byte sequence is provided in either byte array or byte buffer,
 via one of the setInput() methods. The output byte sequence is
 written to the output byte array or byte buffer passed to the
 deflate() methods.
 
 The following code fragment demonstrates a trivial compression
 and decompression of a string using Deflater and
 Inflater.
 
// Encode a String into bytes
String inputString = "blahblahblah\u20AC\u20AC";
byte[] input = inputString.getBytes(StandardCharsets.UTF_8);
// Compress the bytes
ByteArrayOutputStream compressedBaos = new ByteArrayOutputStream();
Deflater compressor = new Deflater();
try {
    compressor.setInput(input);
    // Let the compressor know that the complete input
    // has been made available
    compressor.finish();
    // Keep compressing the input till the compressor
    // is finished compressing
    while (!compressor.finished()) {
        // Use some reasonable size for the temporary buffer
        // based on the data being compressed
        byte[] tmpBuffer = new byte[100];
        int numCompressed = compressor.deflate(tmpBuffer);
        // Copy over the compressed bytes from the temporary
        // buffer into the final byte array
        compressedBaos.write(tmpBuffer, 0, numCompressed);
    }
} finally {
    // Release the resources held by the compressor
    compressor.end();
}
// Decompress the bytes
Inflater decompressor = new Inflater();
ByteArrayOutputStream decompressedBaos = new ByteArrayOutputStream();
try {
    byte[] compressed = compressedBaos.toByteArray();
    decompressor.setInput(compressed, 0, compressed.length);
    while (!decompressor.finished()) {
        // Use some reasonable size for the temporary buffer,
        // based on the data being decompressed; in this example,
        // we use a small buffer size
        byte[] tmpBuffer = new byte[100];
        int numDecompressed = 0;
        try {
            numDecompressed = decompressor.inflate(tmpBuffer);
        } catch (DataFormatException dfe) {
            // Handle the exception suitably, in this example
            // we just rethrow it
            throw new RuntimeException(dfe);
        }
        // Copy over the decompressed bytes from the temporary
        // buffer into the final byte array
        decompressedBaos.write(tmpBuffer, 0, numDecompressed);
    }
} finally {
    // Release the resources held by the decompressor
    decompressor.end();
}
// Decode the bytes into a String
String outputString = decompressedBaos.toString(StandardCharsets.UTF_8);
- API Note:
- To release resources used by this Deflater, theend()method should be called explicitly. Subclasses are responsible for the cleanup of resources acquired by the subclass. Subclasses that overrideObject.finalize()in order to perform cleanup should be modified to use alternative cleanup mechanisms such asCleanerand remove the overridingfinalizemethod.
- Since:
- 1.1
- See Also:
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Field SummaryFieldsModifier and TypeFieldDescriptionstatic final intCompression level for best compression.static final intCompression level for fastest compression.static final intDefault compression level.static final intDefault compression strategy.static final intCompression method for the deflate algorithm (the only one currently supported).static final intCompression strategy best used for data consisting mostly of small values with a somewhat random distribution.static final intCompression flush mode used to flush out all pending output and reset the deflater.static final intCompression strategy for Huffman coding only.static final intCompression level for no compression.static final intCompression flush mode used to achieve best compression result.static final intCompression flush mode used to flush out all pending output; may degrade compression for some compression algorithms.
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Constructor SummaryConstructors
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Method SummaryModifier and TypeMethodDescriptionintdeflate(byte[] output) Compresses the input data and fills specified buffer with compressed data.intdeflate(byte[] output, int off, int len) Compresses the input data and fills specified buffer with compressed data.intdeflate(byte[] output, int off, int len, int flush) Compresses the input data and fills the specified buffer with compressed data.intdeflate(ByteBuffer output) Compresses the input data and fills specified buffer with compressed data.intdeflate(ByteBuffer output, int flush) Compresses the input data and fills the specified buffer with compressed data.voidend()Closes the compressor and discards any unprocessed input.voidfinish()When called, indicates that compression should end with the current contents of the input buffer.booleanfinished()Returns true if the end of the compressed data output stream has been reached.intgetAdler()Returns the ADLER-32 value of the uncompressed data.longReturns the total number of uncompressed bytes input so far.longReturns the total number of compressed bytes output so far.intDeprecated.intDeprecated.UsegetBytesWritten()insteadbooleanReturns true if no data remains in the input buffer.voidreset()Resets deflater so that a new set of input data can be processed.voidsetDictionary(byte[] dictionary) Sets preset dictionary for compression.voidsetDictionary(byte[] dictionary, int off, int len) Sets preset dictionary for compression.voidsetDictionary(ByteBuffer dictionary) Sets preset dictionary for compression.voidsetInput(byte[] input) Sets input data for compression.voidsetInput(byte[] input, int off, int len) Sets input data for compression.voidsetInput(ByteBuffer input) Sets input data for compression.voidsetLevel(int level) Sets the compression level to the specified value.voidsetStrategy(int strategy) Sets the compression strategy to the specified value.
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Field Details- 
DEFLATEDpublic static final int DEFLATEDCompression method for the deflate algorithm (the only one currently supported).- See Also:
 
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NO_COMPRESSIONpublic static final int NO_COMPRESSIONCompression level for no compression.- See Also:
 
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BEST_SPEEDpublic static final int BEST_SPEEDCompression level for fastest compression.- See Also:
 
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BEST_COMPRESSIONpublic static final int BEST_COMPRESSIONCompression level for best compression.- See Also:
 
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DEFAULT_COMPRESSIONpublic static final int DEFAULT_COMPRESSIONDefault compression level.- See Also:
 
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FILTEREDpublic static final int FILTEREDCompression strategy best used for data consisting mostly of small values with a somewhat random distribution. Forces more Huffman coding and less string matching.- See Also:
 
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HUFFMAN_ONLYpublic static final int HUFFMAN_ONLYCompression strategy for Huffman coding only.- See Also:
 
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DEFAULT_STRATEGYpublic static final int DEFAULT_STRATEGYDefault compression strategy.- See Also:
 
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NO_FLUSHpublic static final int NO_FLUSHCompression flush mode used to achieve best compression result.- Since:
- 1.7
- See Also:
 
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SYNC_FLUSHpublic static final int SYNC_FLUSHCompression flush mode used to flush out all pending output; may degrade compression for some compression algorithms.- Since:
- 1.7
- See Also:
 
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FULL_FLUSHpublic static final int FULL_FLUSHCompression flush mode used to flush out all pending output and reset the deflater. Using this mode too often can seriously degrade compression.- Since:
- 1.7
- See Also:
 
 
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Constructor Details- 
Deflaterpublic Deflater(int level, boolean nowrap) Creates a new compressor using the specified compression level. If 'nowrap' is true then the ZLIB header and checksum fields will not be used in order to support the compression format used in both GZIP and PKZIP.- Parameters:
- level- the compression level (0-9)
- nowrap- if true then use GZIP compatible compression
 
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Deflaterpublic Deflater(int level) Creates a new compressor using the specified compression level. Compressed data will be generated in ZLIB format.- Parameters:
- level- the compression level (0-9)
 
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Deflaterpublic Deflater()Creates a new compressor with the default compression level. Compressed data will be generated in ZLIB format.
 
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Method Details- 
setInputpublic void setInput(byte[] input, int off, int len) Sets input data for compression.One of the setInput()methods should be called wheneverneedsInput()returns true indicating that more input data is required.- Parameters:
- input- the input data bytes
- off- the start offset of the data
- len- the length of the data
- See Also:
 
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setInputpublic void setInput(byte[] input) Sets input data for compression.One of the setInput()methods should be called wheneverneedsInput()returns true indicating that more input data is required.- Parameters:
- input- the input data bytes
- See Also:
 
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setInputSets input data for compression.One of the setInput()methods should be called wheneverneedsInput()returns true indicating that more input data is required.The given buffer's position will be advanced as deflate operations are performed, up to the buffer's limit. The input buffer may be modified (refilled) between deflate operations; doing so is equivalent to creating a new buffer and setting it with this method. Modifying the input buffer's contents, position, or limit concurrently with an deflate operation will result in undefined behavior, which may include incorrect operation results or operation failure. - Parameters:
- input- the input data bytes
- Since:
- 11
- See Also:
 
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setDictionarypublic void setDictionary(byte[] dictionary, int off, int len) Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.- Parameters:
- dictionary- the dictionary data bytes
- off- the start offset of the data
- len- the length of the data
- See Also:
 
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setDictionarypublic void setDictionary(byte[] dictionary) Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.- Parameters:
- dictionary- the dictionary data bytes
- See Also:
 
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setDictionarySets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.The bytes in given byte buffer will be fully consumed by this method. On return, its position will equal its limit. - Parameters:
- dictionary- the dictionary data bytes
- Since:
- 11
- See Also:
 
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setStrategypublic void setStrategy(int strategy) Sets the compression strategy to the specified value.If the compression strategy is changed, the next invocation of deflatewill compress the input available so far with the old strategy (and may be flushed); the new strategy will take effect only after that invocation.- Parameters:
- strategy- the new compression strategy
- Throws:
- IllegalArgumentException- if the compression strategy is invalid
 
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setLevelpublic void setLevel(int level) Sets the compression level to the specified value.If the compression level is changed, the next invocation of deflatewill compress the input available so far with the old level (and may be flushed); the new level will take effect only after that invocation.- Parameters:
- level- the new compression level (0-9)
- Throws:
- IllegalArgumentException- if the compression level is invalid
 
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needsInputpublic boolean needsInput()Returns true if no data remains in the input buffer. This can be used to determine if one of thesetInput()methods should be called in order to provide more input.- Returns:
- true if the input data buffer is empty and setInput() should be called in order to provide more input
 
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finishpublic void finish()When called, indicates that compression should end with the current contents of the input buffer.
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finishedpublic boolean finished()Returns true if the end of the compressed data output stream has been reached.- Returns:
- true if the end of the compressed data output stream has been reached
 
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deflatepublic int deflate(byte[] output, int off, int len) Compresses the input data and fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates thatneedsInputshould be called in order to determine if more input data is required.This method uses NO_FLUSHas its compression flush mode. An invocation of this method of the formdeflater.deflate(b, off, len)yields the same result as the invocation ofdeflater.deflate(b, off, len, Deflater.NO_FLUSH).- Parameters:
- output- the buffer for the compressed data
- off- the start offset of the data
- len- the maximum number of bytes of compressed data
- Returns:
- the actual number of bytes of compressed data written to the output buffer
 
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deflatepublic int deflate(byte[] output) Compresses the input data and fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates thatneedsInputshould be called in order to determine if more input data is required.This method uses NO_FLUSHas its compression flush mode. An invocation of this method of the formdeflater.deflate(b)yields the same result as the invocation ofdeflater.deflate(b, 0, b.length, Deflater.NO_FLUSH).- Parameters:
- output- the buffer for the compressed data
- Returns:
- the actual number of bytes of compressed data written to the output buffer
 
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deflateCompresses the input data and fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates thatneedsInputshould be called in order to determine if more input data is required.This method uses NO_FLUSHas its compression flush mode. An invocation of this method of the formdeflater.deflate(output)yields the same result as the invocation ofdeflater.deflate(output, Deflater.NO_FLUSH).- Parameters:
- output- the buffer for the compressed data
- Returns:
- the actual number of bytes of compressed data written to the output buffer
- Throws:
- ReadOnlyBufferException- if the given output buffer is read-only
- Since:
- 11
 
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deflatepublic int deflate(byte[] output, int off, int len, int flush) Compresses the input data and fills the specified buffer with compressed data. Returns actual number of bytes of data compressed.Compression flush mode is one of the following three modes: - NO_FLUSH: allows the deflater to decide how much data to accumulate, before producing output, in order to achieve the best compression (should be used in normal use scenario). A return value of 0 in this flush mode indicates that- needsInput()should be called in order to determine if more input data is required.
- SYNC_FLUSH: all pending output in the deflater is flushed, to the specified output buffer, so that an inflater that works on compressed data can get all input data available so far (In particular the- needsInput()returns- trueafter this invocation if enough output space is provided). Flushing with- SYNC_FLUSHmay degrade compression for some compression algorithms and so it should be used only when necessary.
- FULL_FLUSH: all pending output is flushed out as with- SYNC_FLUSH. The compression state is reset so that the inflater that works on the compressed output data can restart from this point if previous compressed data has been damaged or if random access is desired. Using- FULL_FLUSHtoo often can seriously degrade compression.
 In the case of FULL_FLUSHorSYNC_FLUSH, if the return value islen, the space available in output bufferb, this method should be invoked again with the sameflushparameter and more output space. Make sure thatlenis greater than 6 to avoid flush marker (5 bytes) being repeatedly output to the output buffer every time this method is invoked.If the setInput(ByteBuffer)method was called to provide a buffer for input, the input buffer's position will be advanced by the number of bytes consumed by this operation.- Parameters:
- output- the buffer for the compressed data
- off- the start offset of the data
- len- the maximum number of bytes of compressed data
- flush- the compression flush mode
- Returns:
- the actual number of bytes of compressed data written to the output buffer
- Throws:
- IllegalArgumentException- if the flush mode is invalid
- Since:
- 1.7
 
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deflateCompresses the input data and fills the specified buffer with compressed data. Returns actual number of bytes of data compressed.Compression flush mode is one of the following three modes: - NO_FLUSH: allows the deflater to decide how much data to accumulate, before producing output, in order to achieve the best compression (should be used in normal use scenario). A return value of 0 in this flush mode indicates that- needsInput()should be called in order to determine if more input data is required.
- SYNC_FLUSH: all pending output in the deflater is flushed, to the specified output buffer, so that an inflater that works on compressed data can get all input data available so far (In particular the- needsInput()returns- trueafter this invocation if enough output space is provided). Flushing with- SYNC_FLUSHmay degrade compression for some compression algorithms and so it should be used only when necessary.
- FULL_FLUSH: all pending output is flushed out as with- SYNC_FLUSH. The compression state is reset so that the inflater that works on the compressed output data can restart from this point if previous compressed data has been damaged or if random access is desired. Using- FULL_FLUSHtoo often can seriously degrade compression.
 In the case of FULL_FLUSHorSYNC_FLUSH, if the return value is equal to the remaining space of the buffer, this method should be invoked again with the sameflushparameter and more output space. Make sure that the buffer has at least 6 bytes of remaining space to avoid the flush marker (5 bytes) being repeatedly output to the output buffer every time this method is invoked.On success, the position of the given outputbyte buffer will be advanced by as many bytes as were produced by the operation, which is equal to the number returned by this method.If the setInput(ByteBuffer)method was called to provide a buffer for input, the input buffer's position will be advanced by the number of bytes consumed by this operation.- Parameters:
- output- the buffer for the compressed data
- flush- the compression flush mode
- Returns:
- the actual number of bytes of compressed data written to the output buffer
- Throws:
- IllegalArgumentException- if the flush mode is invalid
- ReadOnlyBufferException- if the given output buffer is read-only
- Since:
- 11
 
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getAdlerpublic int getAdler()Returns the ADLER-32 value of the uncompressed data.- Returns:
- the ADLER-32 value of the uncompressed data
 
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getTotalInDeprecated.UsegetBytesRead()insteadReturns the total number of uncompressed bytes input so far.- Implementation Requirements:
- This method returns the equivalent of (int) getBytesRead()and therefore cannot return the correct value when it is greater thanInteger.MAX_VALUE.
- Returns:
- the total number of uncompressed bytes input so far
 
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getBytesReadpublic long getBytesRead()Returns the total number of uncompressed bytes input so far.- Returns:
- the total (non-negative) number of uncompressed bytes input so far
- Since:
- 1.5
 
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getTotalOutDeprecated.UsegetBytesWritten()insteadReturns the total number of compressed bytes output so far.- Implementation Requirements:
- This method returns the equivalent of (int) getBytesWritten()and therefore cannot return the correct value when it is greater thanInteger.MAX_VALUE.
- Returns:
- the total number of compressed bytes output so far
 
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getBytesWrittenpublic long getBytesWritten()Returns the total number of compressed bytes output so far.- Returns:
- the total (non-negative) number of compressed bytes output so far
- Since:
- 1.5
 
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resetpublic void reset()Resets deflater so that a new set of input data can be processed. Keeps current compression level and strategy settings.
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endpublic void end()Closes the compressor and discards any unprocessed input. This method should be called when the compressor is no longer being used. Once this method is called, the behavior of the Deflater object is undefined.
 
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getBytesRead()instead