Inflater (Java SE 26 & JDK 26)
Description: declaration: module: java.base, package: java.util.zip, class: Inflater
Keywords: java.util.zip.Inflater class

# Class Inflater

java.lang.Object
java.util.zip.Inflater

All Implemented Interfaces:
  `AutoCloseable`

public class Inflater extends Object implements AutoCloseable
This class provides support for general purpose decompression using the popular ZLIB compression library. The ZLIB compression library was initially developed as part of the PNG graphics standard and is not protected by patents. It is fully described in the specifications at the java.util.zip package description.

Unless otherwise noted, passing a `null` argument to a constructor or method in this class will cause a `NullPointerException` to be thrown.

This class inflates sequences of ZLIB compressed bytes. The input byte sequence is provided in either a byte array or a `ByteBuffer`, via one of the `setInput()` methods. The output byte sequence is written to the output byte array or `ByteBuffer` passed to the `inflate()` methods.

To release the resources used by an `Inflater`, an application must close it by invoking its `end()` or `close()` method.

API Note:
  This class implements `AutoCloseable` to facilitate its usage with `try`-with-resources statement. The close() method simply calls `end()`.

  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();
      try (Deflater compressor = new Deflater()) {
          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);
          }
      }

      // Decompress the bytes
      ByteArrayOutputStream decompressedBaos = new ByteArrayOutputStream();
      try (Inflater decompressor = new Inflater()) {
          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);
          }
      }
      // Decode the bytes into a String
      String outputString = decompressedBaos.toString(StandardCharsets.UTF_8);

Since:
  1.1
See Also:
  - `Deflater`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `Inflater()`
  Creates a new decompressor.
  `Inflater(boolean nowrap)`
  Creates a new decompressor.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `close()`
  Closes and releases the resources held by this `Inflater` and discards any unprocessed input.
  `void`
  `end()`
  Closes and releases the resources held by this `Inflater` and discards any unprocessed input.
  `boolean`
  `finished()`
  Returns true if the end of the compressed data stream has been reached.
  `int`
  `getAdler()`
  Returns the ADLER-32 value of the uncompressed data.
  `long`
  `getBytesRead()`
  Returns the total number of compressed bytes input so far.
  `long`
  `getBytesWritten()`
  Returns the total number of uncompressed bytes output so far.
  `int`
  `getRemaining()`
  Returns the total number of bytes remaining in the input buffer.
  `int`
  `getTotalIn()`
  Deprecated.
  Use `getBytesRead()` instead
  `int`
  `getTotalOut()`
  Deprecated.
  Use `getBytesWritten()` instead
  `int`
  `inflate(byte[] output)`
  Uncompresses bytes into specified buffer.
  `int`
  `inflate(byte[] output, int off, int len)`
  Uncompresses bytes into specified buffer.
  `int`
  `inflate(ByteBuffer output)`
  Uncompresses bytes into specified buffer.
  `boolean`
  `needsDictionary()`
  Returns true if a preset dictionary is needed for decompression.
  `boolean`
  `needsInput()`
  Returns true if no data remains in the input buffer.
  `void`
  `reset()`
  Resets inflater so that a new set of input data can be processed.
  `void`
  `setDictionary(byte[] dictionary)`
  Sets the preset dictionary to the given array of bytes.
  `void`
  `setDictionary(byte[] dictionary, int off, int len)`
  Sets the preset dictionary to the given array of bytes.
  `void`
  `setDictionary(ByteBuffer dictionary)`
  Sets the preset dictionary to the bytes in the given buffer.
  `void`
  `setInput(byte[] input)`
  Sets input data for decompression.
  `void`
  `setInput(byte[] input, int off, int len)`
  Sets input data for decompression.
  `void`
  `setInput(ByteBuffer input)`
  Sets input data for decompression.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
  Modifier and Type
  Method
  Description
  `protected Object`
  `clone()`
  Creates and returns a copy of this object.
  `boolean`
  `equals(Object obj)`
  Indicates whether some other object is "equal to" this one.
  `protected void`
  `finalize()`
  Deprecated, for removal: This API element is subject to removal in a future version.
  Finalization is deprecated and subject to removal in a future release.
  `final Class<?>`
  `getClass()`
  Returns the runtime class of this `Object`.
  `int`
  `hashCode()`
  Returns a hash code value for this object.
  `final void`
  `notify()`
  Wakes up a single thread that is waiting on this object's monitor.
  `final void`
  `notifyAll()`
  Wakes up all threads that are waiting on this object's monitor.
  `String`
  `toString()`
  Returns a string representation of the object.
  `final void`
  `wait()`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
  `final void`
  `wait(long timeoutMillis)`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
  `final void`
  `wait(long timeoutMillis, int nanos)`
  Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

- ## Constructor Details

  - ### Inflater

    public Inflater(boolean nowrap)
    Creates a new decompressor. If the parameter 'nowrap' is true then the ZLIB header and checksum fields will not be used. This provides compatibility with the compression format used by both GZIP and PKZIP.

    Note: When using the 'nowrap' option it is also necessary to provide an extra "dummy" byte as input. This is required by the ZLIB native library in order to support certain optimizations.

    Parameters:
      `nowrap` - if true then support GZIP compatible compression

  - ### Inflater

    public Inflater()
    Creates a new decompressor.

- ## Method Details

  - ### setInput

    public void setInput(byte[] input, int off, int len)
    Sets input data for decompression.

    One of the `setInput()` methods should be called whenever `needsInput()` returns true indicating that more input data is required.

    Parameters:
      `input` - the input data bytes
      `off` - the start offset of the input data
      `len` - the length of the input data
    See Also:
      - `needsInput()`

  - ### setInput

    public void setInput(byte[] input)
    Sets input data for decompression.

    One of the `setInput()` methods should be called whenever `needsInput()` returns true indicating that more input data is required.

    Parameters:
      `input` - the input data bytes
    See Also:
      - `needsInput()`

  - ### setInput

    public void setInput(ByteBuffer input)
    Sets input data for decompression.

    One of the `setInput()` methods should be called whenever `needsInput()` returns true indicating that more input data is required.

    The given buffer's position will be advanced as inflate operations are performed, up to the buffer's limit. The input buffer may be modified (refilled) between inflate 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 inflate 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:
      - `needsInput()`

  - ### setDictionary

    public void setDictionary(byte[] dictionary, int off, int len)
    Sets the preset dictionary to the given array of bytes. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.
    Parameters:
      `dictionary` - the dictionary data bytes
      `off` - the start offset of the data
      `len` - the length of the data
    Throws:
      `IllegalStateException` - if the Inflater is closed
    See Also:
      - `needsDictionary()`
      - `getAdler()`

  - ### setDictionary

    public void setDictionary(byte[] dictionary)
    Sets the preset dictionary to the given array of bytes. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.
    Parameters:
      `dictionary` - the dictionary data bytes
    Throws:
      `IllegalStateException` - if the Inflater is closed
    See Also:
      - `needsDictionary()`
      - `getAdler()`

  - ### setDictionary

    public void setDictionary(ByteBuffer dictionary)
    Sets the preset dictionary to the bytes in the given buffer. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.

    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
    Throws:
      `IllegalStateException` - if the Inflater is closed
    Since:
      11
    See Also:
      - `needsDictionary()`
      - `getAdler()`

  - ### getRemaining

    public int getRemaining()
    Returns the total number of bytes remaining in the input buffer. This can be used to find out what bytes still remain in the input buffer after decompression has finished.
    Returns:
      the total number of bytes remaining in the input buffer

  - ### needsInput

    public boolean needsInput()
    Returns true if no data remains in the input buffer. This can be used to determine if one of the `setInput()` methods should be called in order to provide more input.
    Returns:
      true if no data remains in the input buffer

  - ### needsDictionary

    public boolean needsDictionary()
    Returns true if a preset dictionary is needed for decompression.
    Returns:
      true if a preset dictionary is needed for decompression
    See Also:
      - `setDictionary(byte[], int, int)`

  - ### finished

    public boolean finished()
    Returns true if the end of the compressed data stream has been reached.
    Returns:
      true if the end of the compressed data stream has been reached

  - ### inflate

    public int inflate(byte[] output, int off, int len) throws DataFormatException
    Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the latter case, getAdler() can be used to get the Adler-32 value of the dictionary required.

    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, even in the event that a `DataFormatException` is thrown.

    The remaining byte count will be reduced by the number of consumed input bytes. If the `setInput(ByteBuffer)` method was called to provide a buffer for input, the input buffer's position will be advanced the number of consumed bytes.

    These byte totals, as well as the total bytes read and the total bytes written values, will be updated even in the event that a `DataFormatException` is thrown to reflect the amount of data consumed and produced before the exception occurred.

    Parameters:
      `output` - the buffer for the uncompressed data
      `off` - the start offset of the data
      `len` - the maximum number of uncompressed bytes
    Returns:
      the actual number of uncompressed bytes
    Throws:
      `DataFormatException` - if the compressed data format is invalid
      `IllegalStateException` - if the Inflater is closed
    See Also:
      - `needsInput()`
      - `needsDictionary()`

  - ### inflate

    public int inflate(byte[] output) throws DataFormatException
    Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the latter case, getAdler() can be used to get the Adler-32 value of the dictionary required.

    The remaining byte count will be reduced by the number of consumed input bytes. If the `setInput(ByteBuffer)` method was called to provide a buffer for input, the input buffer's position will be advanced the number of consumed bytes.

    These byte totals, as well as the total bytes read and the total bytes written values, will be updated even in the event that a `DataFormatException` is thrown to reflect the amount of data consumed and produced before the exception occurred.

    Parameters:
      `output` - the buffer for the uncompressed data
    Returns:
      the actual number of uncompressed bytes
    Throws:
      `DataFormatException` - if the compressed data format is invalid
      `IllegalStateException` - if the Inflater is closed
    See Also:
      - `needsInput()`
      - `needsDictionary()`

  - ### inflate

    public int inflate(ByteBuffer output) throws DataFormatException
    Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the latter case, getAdler() can be used to get the Adler-32 value of the dictionary required.

    On success, the position of the given `output` byte buffer will be advanced by as many bytes as were produced by the operation, which is equal to the number returned by this method. Note that the position of the `output` buffer will be advanced even in the event that a `DataFormatException` is thrown.

    The remaining byte count will be reduced by the number of consumed input bytes. If the `setInput(ByteBuffer)` method was called to provide a buffer for input, the input buffer's position will be advanced the number of consumed bytes.

    These byte totals, as well as the total bytes read and the total bytes written values, will be updated even in the event that a `DataFormatException` is thrown to reflect the amount of data consumed and produced before the exception occurred.

    Parameters:
      `output` - the buffer for the uncompressed data
    Returns:
      the actual number of uncompressed bytes
    Throws:
      `DataFormatException` - if the compressed data format is invalid
      `ReadOnlyBufferException` - if the given output buffer is read-only
      `IllegalStateException` - if the Inflater is closed
    Since:
      11
    See Also:
      - `needsInput()`
      - `needsDictionary()`

  - ### getAdler

    public int getAdler()
    Returns the ADLER-32 value of the uncompressed data.
    Returns:
      the ADLER-32 value of the uncompressed data
    Throws:
      `IllegalStateException` - if the Inflater is closed

  - ### getTotalIn

    @Deprecated(since="23") public int getTotalIn()
    Deprecated.
    Use `getBytesRead()` instead
    Returns the total number of compressed 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 than `Integer.MAX_VALUE`.
    Returns:
      the total number of compressed bytes input so far
    Throws:
      `IllegalStateException` - if the Inflater is closed

  - ### getBytesRead

    public long getBytesRead()
    Returns the total number of compressed bytes input so far.
    Returns:
      the total (non-negative) number of compressed bytes input so far
    Throws:
      `IllegalStateException` - if the Inflater is closed
    Since:
      1.5

  - ### getTotalOut

    @Deprecated(since="23") public int getTotalOut()
    Deprecated.
    Use `getBytesWritten()` instead
    Returns the total number of uncompressed 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 than `Integer.MAX_VALUE`.
    Returns:
      the total number of uncompressed bytes output so far
    Throws:
      `IllegalStateException` - if the Inflater is closed

  - ### getBytesWritten

    public long getBytesWritten()
    Returns the total number of uncompressed bytes output so far.
    Returns:
      the total (non-negative) number of uncompressed bytes output so far
    Throws:
      `IllegalStateException` - if the Inflater is closed
    Since:
      1.5

  - ### reset

    public void reset()
    Resets inflater so that a new set of input data can be processed.
    Throws:
      `IllegalStateException` - if the Inflater is closed

  - ### end

    public void end()
    Closes and releases the resources held by this `Inflater` and discards any unprocessed input.

    If the `Inflater` is already closed then invoking this method has no effect.

    Implementation Requirements:
      Subclasses should override this method to clean up the resources acquired by the subclass.
    See Also:
      - `close()`

  - ### close

    public void close()
    Closes and releases the resources held by this `Inflater` and discards any unprocessed input.
    Specified by:
      `close` in interface `AutoCloseable`
    Implementation Requirements:
      This method calls the `end()` method.
    Since:
      25