Java : Inflater (ZIP) with Examples

Inflater (Java SE 19 & JDK 19) API Examples.
You will find code examples on most Inflater methods.

Summary

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.

Class diagram

Please see also : InflaterInputStream, InflaterOutputStream

// --------
// Compression
final var deflater = new Deflater();
final var compressed = new byte[15];
int compressedLength;
try {
    final var input = "aaaaa".getBytes();

    // [97, 97, 97, 97, 97]
    System.out.println(Arrays.toString(input));

    deflater.setInput(input);
    deflater.finish();

    compressedLength = deflater.deflate(compressed);

    // 11
    System.out.println(compressedLength);

    // [120, -100, 75, 76, 4, 2, 0, 5, -76, 1, -26, 0, 0, 0, 0]
    System.out.println(Arrays.toString(compressed));
} finally {
    deflater.end();
}

// --------
// Decompression
final var inflater = new Inflater();
try {
    inflater.setInput(compressed, 0, compressedLength);

    final var decompressed = new byte[10];
    final var decompressedLength = inflater.inflate(decompressed);

    // 5
    System.out.println(decompressedLength);

    // [97, 97, 97, 97, 97, 0, 0, 0, 0, 0]
    System.out.println(Arrays.toString(decompressed));

    // aaaaa
    System.out.println(new String(decompressed, 0, decompressedLength));
} finally {
    inflater.end();
}

The deflate method is here.

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    System.out.println("-- inflate --");
    while (!inflater.finished()) {
        final var output = new byte[5];
        final var length = inflater.inflate(output);
        System.out.printf("length=%d : %s%n", length, new String(output, 0, length));
    }
} finally {
    inflater.end();
}

// Result
// ↓
//-- inflate --
//length=5 : aaaXX
//length=5 : XbbbY
//length=2 : YY

Helper method for code examples

Code examples on this page use the helper method below.

// Compress a string.
public byte[] deflate(String str) throws IOException {
    final var out = new ByteArrayOutputStream();
    try (final var dos = new DeflaterOutputStream(out)) {
        dos.write(str.getBytes());
    }

    return out.toByteArray();
}

Constructors

Inflater ()

Creates a new decompressor.

The deflate method is here.

final var input = deflate("aaaaa");

// [120, -100, 75, 76, 4, 2, 0, 5, -76, 1, -26]
System.out.println(Arrays.toString(input));

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    final var output = new byte[10];
    final var length = inflater.inflate(output);

    // 5
    System.out.println(length);

    // [97, 97, 97, 97, 97, 0, 0, 0, 0, 0]
    System.out.println(Arrays.toString(output));

    // aaaaa
    System.out.println(new String(output, 0, length));
} finally {
    inflater.end();
}

Inflater (boolean nowrap)

Creates a new decompressor.

final var deflater = new Deflater(Deflater.DEFAULT_COMPRESSION, true);
final var compressed = new byte[10];
int compressLength;
try {
    final var input = "aaaXXX".getBytes();

    // [97, 97, 97, 88, 88, 88]
    System.out.println(Arrays.toString(input));

    deflater.setInput(input);
    deflater.finish();

    compressLength = deflater.deflate(compressed);

    // 8
    System.out.println(compressLength);

    // [75, 76, 76, -116, -120, -120, 0, 0, 0, 0]
    System.out.println(Arrays.toString(compressed));
} finally {
    deflater.end();
}

final var inflater = new Inflater(true);
try {
    inflater.setInput(compressed, 0, compressLength);

    final var uncompressed = new byte[10];
    final var uncompressedLength = inflater.inflate(uncompressed);

    // 6
    System.out.println(uncompressedLength);

    // [97, 97, 97, 88, 88, 88, 0, 0, 0, 0]
    System.out.println(Arrays.toString(uncompressed));

    // aaaXXX
    System.out.println(new String(uncompressed, 0, uncompressedLength));
} finally {
    inflater.end();
}

Methods

void end ()

Closes the decompressor and discards any unprocessed input.

Please see inflate(byte[] output).

boolean finished ()

Returns true if the end of the compressed data stream has been reached.

Please see inflate(byte[] output).

int getAdler ()

Returns the ADLER-32 value of the uncompressed data.

The deflate method is here.

final var input = deflate("aaaaa");

// [120, -100, 75, 76, 4, 2, 0, 5, -76, 1, -26]
System.out.println(Arrays.toString(input));

final var inflater = new Inflater();
try {
    inflater.setInput(input);
    System.out.println(inflater.getAdler()); // 1

    final var output = new byte[10];
    System.out.println(inflater.inflate(output)); // 5

    // [97, 97, 97, 97, 97, 0, 0, 0, 0, 0]
    System.out.println(Arrays.toString(output));

    System.out.println(inflater.getAdler()); // 95683046
} finally {
    inflater.end();
}

long getBytesRead ()

Returns the total number of compressed bytes input so far.

The deflate method is here.

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    System.out.println("-- inflate --");
    while (!inflater.finished()) {
        final var output = new byte[5];
        final var length = inflater.inflate(output);
        final var total = inflater.getBytesRead();
        System.out.printf("length=%d : total=%2d : %s%n",
                length, total, new String(output, 0, length));
    }
} finally {
    inflater.end();
}

// Result
// ↓
//-- inflate --
//length=5 : total= 9 : aaaXX
//length=5 : total=14 : XbbbY
//length=2 : total=20 : YY

long getBytesWritten ()

Returns the total number of uncompressed bytes output so far.

The deflate method is here.

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    System.out.println("-- inflate --");
    while (!inflater.finished()) {
        final var output = new byte[5];
        final var length = inflater.inflate(output);
        final var total = inflater.getBytesWritten();
        System.out.printf("length=%d : total=%2d : %s%n",
                length, total, new String(output, 0, length));
    }
} finally {
    inflater.end();
}

// Result
// ↓
//-- inflate --
//length=5 : total= 5 : aaaXX
//length=5 : total=10 : XbbbY
//length=2 : total=12 : YY

int getRemaining ()

Returns the total number of bytes remaining in the input buffer.

The deflate method is here.

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    System.out.println("-- inflate --");
    while (!inflater.finished()) {
        final var output = new byte[5];
        final var length = inflater.inflate(output);
        final var total = inflater.getRemaining();
        System.out.printf("length=%d : total=%2d : %s%n",
                length, total, new String(output, 0, length));
    }
} finally {
    inflater.end();
}

// Result
// ↓
//-- inflate --
//length=5 : total=11 : aaaXX
//length=5 : total= 6 : XbbbY
//length=2 : total= 0 : YY

int getTotalIn ()

Returns the total number of compressed bytes input so far.

The deflate method is here.

Please see also : getBytesRead()

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    System.out.println("-- inflate --");
    while (!inflater.finished()) {
        final var output = new byte[5];
        final var length = inflater.inflate(output);
        final var total = inflater.getTotalIn();
        System.out.printf("length=%d : total=%2d : %s%n",
                length, total, new String(output, 0, length));
    }
} finally {
    inflater.end();
}

// Result
// ↓
//-- inflate --
//length=5 : total= 9 : aaaXX
//length=5 : total=14 : XbbbY
//length=2 : total=20 : YY

int getTotalOut ()

Returns the total number of uncompressed bytes output so far.

The deflate method is here.

Please see also : getBytesWritten()

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    System.out.println("-- inflate --");
    while (!inflater.finished()) {
        final var output = new byte[5];
        final var length = inflater.inflate(output);
        final var total = inflater.getTotalOut();
        System.out.printf("length=%d : total=%2d : %s%n",
                length, total, new String(output, 0, length));
    }
} finally {
    inflater.end();
}

// Result
// ↓
//-- inflate --
//length=5 : total= 5 : aaaXX
//length=5 : total=10 : XbbbY
//length=2 : total=12 : YY

int inflate (byte[] output)

Uncompresses bytes into specified buffer.

The deflate method is here.

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    System.out.println("-- inflate --");
    while (!inflater.finished()) {
        final var output = new byte[5];
        final var length = inflater.inflate(output);
        System.out.printf("length=%d : %s%n", length, new String(output, 0, length));
    }
} finally {
    inflater.end();
}

// Result
// ↓
//-- inflate --
//length=5 : aaaXX
//length=5 : XbbbY
//length=2 : YY

int inflate (byte[] output, int off, int len)

Uncompresses bytes into specified buffer.

The deflate method is here.

final var input = deflate("aaaaa");

// [120, -100, 75, 76, 4, 2, 0, 5, -76, 1, -26]
System.out.println(Arrays.toString(input));

// 11
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    final var output1 = new byte[10];
    System.out.println(inflater.inflate(output1)); // 5

    // [97, 97, 97, 97, 97, 0, 0, 0, 0, 0]
    System.out.println(Arrays.toString(output1));

    inflater.reset();
    inflater.setInput(input);

    final var output2 = new byte[10];
    System.out.println(inflater.inflate(output2, 2, 7)); // 5

    // [0, 0, 97, 97, 97, 97, 97, 0, 0, 0]
    System.out.println(Arrays.toString(output2));
} finally {
    inflater.end();
}

int inflate (ByteBuffer output)

Uncompresses bytes into specified buffer.

The deflate method is here.

final var input = deflate("aaaaa");

// [120, -100, 75, 76, 4, 2, 0, 5, -76, 1, -26]
System.out.println(Arrays.toString(input));

// 11
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    final var output = ByteBuffer.allocate(10);
    final var length = inflater.inflate(output);

    System.out.println(length); // 5
    System.out.println(output); // java.nio.HeapByteBuffer[pos=5 lim=10 cap=10]

    // [97, 97, 97, 97, 97, 0, 0, 0, 0, 0]
    System.out.println(Arrays.toString(output.array()));

    // aaaaa
    System.out.println(new String(output.array(), 0, length));
} finally {
    inflater.end();
}

boolean needsDictionary ()

Returns true if a preset dictionary is needed for decompression.

Please see setDictionary(byte[] dictionary).

boolean needsInput ()

Returns true if no data remains in the input buffer.

The deflate method is here.

final var input = deflate("aaaaXXXX");

// [120, -100, 75, 76, 76, 76, -116, 0, 2, 0, 13, 82, 2, -27]
System.out.println(Arrays.toString(input));

// 14
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    final var output1 = new byte[5];
    final var length1 = inflater.inflate(output1);

    System.out.println(length1); // 5
    System.out.println(new String(output1, 0, length1)); // aaaaX
    System.out.println(inflater.needsInput()); // false

    final var output2 = new byte[5];
    final var length2 = inflater.inflate(output2);

    System.out.println(length2); // 3
    System.out.println(new String(output2, 0, length2)); // XXX
    System.out.println(inflater.needsInput()); // true
} finally {
    inflater.end();
}

void reset ()

Resets inflater so that a new set of input data can be processed.

Please see inflate(byte[] output, int off, int len).

void setDictionary (byte[] dictionary)

Sets the preset dictionary to the given array of bytes.

final var input = "abcXYZabcXYZabcXYZ".getBytes();
final var dictionary = "abcXYZ".getBytes();

// --------
// Compression
final var deflater = new Deflater();
final var compressed = new byte[15];
int compressedLength;
try {
    deflater.setDictionary(dictionary);
    deflater.setInput(input);
    deflater.finish();

    compressedLength = deflater.deflate(compressed);
    System.out.println(compressedLength); // 14

    // [120, -69, 7, -42, 2, 50, 75, -60, 32, 1, 62, -12, 6, -108, 0]
    System.out.println(Arrays.toString(compressed));
} finally {
    deflater.end();
}

// --------
// Decompression
final var inflater = new Inflater();
try {
    inflater.setInput(compressed, 0, compressedLength);

    final var decompressed = new byte[20];
    System.out.println(inflater.inflate(decompressed)); // 0
    System.out.println(inflater.needsDictionary()); // true

    inflater.setDictionary(dictionary);

    final int decompressedLength = inflater.inflate(decompressed);
    System.out.println(decompressedLength); // 18

    // [97, 98, 99, 88, 89, 90, 97, 98, 99, 88, 89, 90, 97, 98, 99, 88, 89, 90, 0, 0]
    System.out.println(Arrays.toString(decompressed));

    // abcXYZabcXYZabcXYZ
    System.out.println(new String(decompressed, 0, decompressedLength));
} finally {
    inflater.end();
}

void setDictionary (byte[] dictionary, int off, int len)

Sets the preset dictionary to the given array of bytes.

final var input = "abcXYZabcXYZabcXYZ".getBytes();
final var dictionary = "abcXYZ".getBytes();

// --------
// Compression
final var deflater = new Deflater();
final var compressed = new byte[20];
int compressedLength;
try {
    deflater.setDictionary(dictionary, 1, 4);
    deflater.setInput(input);
    deflater.finish();

    compressedLength = deflater.deflate(compressed);
    System.out.println(compressedLength); // 18

    // [120, -69, 3, -66, 1, 119, 75, 76, 2, 18, 81, -56, 36, 0, 62, -12, 6, -108, 0, 0]
    System.out.println(Arrays.toString(compressed));
} finally {
    deflater.end();
}

// --------
// Decompression
final var inflater = new Inflater();
try {
    inflater.setInput(compressed, 0, compressedLength);

    final var decompressed = new byte[20];
    System.out.println(inflater.inflate(decompressed)); // 0
    System.out.println(inflater.needsDictionary()); // true

    inflater.setDictionary(dictionary, 1, 4);

    final int decompressedLength = inflater.inflate(decompressed);
    System.out.println(decompressedLength); // 18

    // [97, 98, 99, 88, 89, 90, 97, 98, 99, 88, 89, 90, 97, 98, 99, 88, 89, 90, 0, 0]
    System.out.println(Arrays.toString(decompressed));

    // abcXYZabcXYZabcXYZ
    System.out.println(new String(decompressed, 0, decompressedLength));
} finally {
    inflater.end();
}

void setDictionary (ByteBuffer dictionary)

Sets the preset dictionary to the bytes in the given buffer.

final var input = "abcXYZabcXYZabcXYZ".getBytes();
final var dictionary = "abcXYZ".getBytes();

// --------
// Compression
final var deflater = new Deflater();
final var compressed = new byte[15];
int compressedLength;
try {
    deflater.setDictionary(ByteBuffer.wrap(dictionary));
    deflater.setInput(input);
    deflater.finish();

    compressedLength = deflater.deflate(compressed);
    System.out.println(compressedLength); // 14

    // [120, -69, 7, -42, 2, 50, 75, -60, 32, 1, 62, -12, 6, -108, 0]
    System.out.println(Arrays.toString(compressed));
} finally {
    deflater.end();
}

// --------
// Decompression
final var inflater = new Inflater();
try {
    inflater.setInput(compressed, 0, compressedLength);

    final var decompressed = new byte[20];
    System.out.println(inflater.inflate(decompressed)); // 0
    System.out.println(inflater.needsDictionary()); // true

    inflater.setDictionary(ByteBuffer.wrap(dictionary));

    final int decompressedLength = inflater.inflate(decompressed);
    System.out.println(decompressedLength); // 18

    // [97, 98, 99, 88, 89, 90, 97, 98, 99, 88, 89, 90, 97, 98, 99, 88, 89, 90, 0, 0]
    System.out.println(Arrays.toString(decompressed));

    // abcXYZabcXYZabcXYZ
    System.out.println(new String(decompressed, 0, decompressedLength));
} finally {
    inflater.end();
}

void setInput (byte[] input)

Sets input data for decompression.

The deflate method is here.

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(Arrays.copyOf(input, 10));

    final var output1 = new byte[10];
    final var length1 = inflater.inflate(output1);

    // 7
    System.out.println(length1);

    // [97, 97, 97, 88, 88, 88, 98, 0, 0, 0]
    System.out.println(Arrays.toString(output1));

    // aaaXXXb
    System.out.println(new String(output1, 0, length1));

    inflater.setInput(Arrays.copyOfRange(input, 10, 20));

    final var output2 = new byte[10];
    final var length2 = inflater.inflate(output2);

    // 5
    System.out.println(length2);

    // [98, 98, 89, 89, 89, 0, 0, 0, 0, 0]
    System.out.println(Arrays.toString(output2));

    // bbYYY
    System.out.println(new String(output2, 0, length2));
} finally {
    inflater.end();
}

void setInput (byte[] input, int off, int len)

Sets input data for decompression.

The deflate method is here.

final var input = deflate("aaaXXXbbbYYY");

// [120, -100, 75, 76, 76, -116, -120, -120, 72, 74, 74,
//  -118, -116, -116, 4, 0, 28, -95, 4, 93]
System.out.println(Arrays.toString(input));

// 20
System.out.println(input.length);

final var inflater = new Inflater();
try {
    inflater.setInput(input, 0, 12);

    final var output1 = new byte[10];
    final var length1 = inflater.inflate(output1);

    // 9
    System.out.println(length1);

    // [97, 97, 97, 88, 88, 88, 98, 98, 98, 0]
    System.out.println(Arrays.toString(output1));

    // aaaXXXbbb
    System.out.println(new String(output1, 0, length1));

    inflater.setInput(input, 12, 8);

    final var output2 = new byte[10];
    final var length2 = inflater.inflate(output2);

    // 3
    System.out.println(length2);

    // [89, 89, 89, 0, 0, 0, 0, 0, 0, 0]
    System.out.println(Arrays.toString(output2));

    // YYY
    System.out.println(new String(output2, 0, length2));
} finally {
    inflater.end();
}

void setInput (ByteBuffer input)

Sets input data for decompression.

The deflate method is here.

final var input = ByteBuffer.wrap(deflate("aaaaa"));
System.out.println(input); // java.nio.HeapByteBuffer[pos=0 lim=11 cap=11]

// [120, -100, 75, 76, 4, 2, 0, 5, -76, 1, -26]
System.out.println(Arrays.toString(input.array()));

final var inflater = new Inflater();
try {
    inflater.setInput(input);

    final var output = new byte[10];
    final var length = inflater.inflate(output);

    // 5
    System.out.println(length);

    // [97, 97, 97, 97, 97, 0, 0, 0, 0, 0]
    System.out.println(Arrays.toString(output));

    // aaaaa
    System.out.println(new String(output, 0, length));
} finally {
    inflater.end();
}

API Examples

Java : Inflater (ZIP) with Examples

Summary

Helper method for code examples

Constructors

Inflater ()

Inflater (boolean nowrap)

Methods

void end ()

boolean finished ()

int getAdler ()

long getBytesRead ()

long getBytesWritten ()

int getRemaining ()

int getTotalIn ()

int getTotalOut ()

int inflate (byte[] output)

int inflate (byte[] output, int off, int len)

int inflate (ByteBuffer output)

boolean needsDictionary ()

boolean needsInput ()

void reset ()

void setDictionary (byte[] dictionary)

void setDictionary (byte[] dictionary, int off, int len)

void setDictionary (ByteBuffer dictionary)

void setInput (byte[] input)

void setInput (byte[] input, int off, int len)

void setInput (ByteBuffer input)

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