Class ZipInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

java.util.zip.InflaterInputStream

java.util.zip.ZipInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

Direct Known Subclasses:

JarInputStream

public class ZipInputStream
extends InflaterInputStream

An input stream for reading compressed and uncompressed ZIP file entries from a stream of bytes in the ZIP file format.

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

Reading Zip File Entries

The getNextEntry() method is used to read the next ZIP file entry (Local file (LOC) header record in the ZIP format) and position the stream at the entry's file data. The file data may read using one of the ZipInputStream read methods such as read or readAllBytes(). For example:

  Path jar = Path.of("foo.jar");
  try (InputStream is = Files.newInputStream(jar);
       ZipInputStream zis = new ZipInputStream(is)) {
      ZipEntry ze;
      while ((ze = zis.getNextEntry()) != null) {
         var bytes = zis.readAllBytes();
         System.out.printf("Entry: %s, bytes read: %s%n", ze.getName(),
                 bytes.length);
      }
  }

API Note:

The LOC header contains metadata about the ZIP file entry. ZipInputStream does not read the Central directory (CEN) header for the entry and therefore will not have access to its metadata such as the external file attributes. ZipFile may be used when the information stored within the CEN header is required.

Since:

1.1

Field Summary

Fields

Modifier and Type	Field	Description
static final int	CENATT	Central directory (CEN) header internal file attributes field offset.
static final int	CENATX	Central directory (CEN) header external file attributes field offset.
static final int	CENCOM	Central directory (CEN) header comment length field offset.
static final int	CENCRC	Central directory (CEN) header uncompressed file crc-32 value field offset.
static final int	CENDSK	Central directory (CEN) header disk number start field offset.
static final int	CENEXT	Central directory (CEN) header extra field length field offset.
static final int	CENFLG	Central directory (CEN) header encrypt, decrypt flags field offset.
static final int	CENHDR	Central directory (CEN) header size in bytes (including signature).
static final int	CENHOW	Central directory (CEN) header compression method field offset.
static final int	CENLEN	Central directory (CEN) header uncompressed size field offset.
static final int	CENNAM	Central directory (CEN) header filename length field offset.
static final int	CENOFF	Central directory (CEN) header LOC header offset field offset.
static final long	CENSIG	Central directory (CEN) header signature.
static final int	CENSIZ	Central directory (CEN) header compressed size field offset.
static final int	CENTIM	Central directory (CEN) header modification time field offset.
static final int	CENVEM	Central directory (CEN) header version made by field offset.
static final int	CENVER	Central directory (CEN) header version needed to extract field offset.
static final int	ENDCOM	End of central directory (END) header ZIP file comment length field offset.
static final int	ENDHDR	End of central directory (END) header size in bytes (including signature).
static final int	ENDOFF	End of central directory (END) header offset for the first CEN header field offset.
static final long	ENDSIG	End of central directory (END) header signature.
static final int	ENDSIZ	End of central directory (END) header central directory size in bytes field offset.
static final int	ENDSUB	End of central directory (END) header number of entries on this disk field offset.
static final int	ENDTOT	End of central directory (END) header total number of entries field offset.
static final int	EXTCRC	Extra local (EXT) header uncompressed file crc-32 value field offset.
static final int	EXTHDR	Extra local (EXT) header size in bytes (including signature).
static final int	EXTLEN	Extra local (EXT) header uncompressed size field offset.
static final long	EXTSIG	Extra local (EXT) header signature.
static final int	EXTSIZ	Extra local (EXT) header compressed size field offset.
static final int	LOCCRC	Local file (LOC) header uncompressed file crc-32 value field offset.
static final int	LOCEXT	Local file (LOC) header extra field length field offset.
static final int	LOCFLG	Local file (LOC) header general purpose bit flag field offset.
static final int	LOCHDR	Local file (LOC) header size in bytes (including signature).
static final int	LOCHOW	Local file (LOC) header compression method field offset.
static final int	LOCLEN	Local file (LOC) header uncompressed size field offset.
static final int	LOCNAM	Local file (LOC) header filename length field offset.
static final long	LOCSIG	Local file (LOC) header signature.
static final int	LOCSIZ	Local file (LOC) header compressed size field offset.
static final int	LOCTIM	Local file (LOC) header modification time field offset.
static final int	LOCVER	Local file (LOC) header version needed to extract field offset.

Fields declared in class java.util.zip.InflaterInputStream

buf, inf, len

Fields declared in class java.io.FilterInputStream

in

Constructor Summary

Constructors

Constructor	Description
ZipInputStream(InputStream in)	Creates a new ZIP input stream.
ZipInputStream(InputStream in, Charset charset)	Creates a new ZIP input stream.

Method Summary

Modifier and Type	Method	Description
int	available()	Returns 0 when end of stream is detected for the current ZIP entry or closeEntry() has been called on the current ZIP entry, otherwise returns 1.
void	close()	Closes this input stream and releases any system resources associated with the stream.
void	closeEntry()	Closes the current ZIP entry and positions the stream for reading the next entry.
protected ZipEntry	createZipEntry(String name)	Creates a new ZipEntry object for the specified entry name.
ZipEntry	getNextEntry()	Reads the next ZIP file entry and positions the stream at the beginning of the entry data.
int	read()	Reads the next byte of data from the input stream for the current ZIP entry.
int	read(byte[] b, int off, int len)	Reads the requested number of bytes from the input stream into the given byte array for the current ZIP entry returning the number of inflated bytes.
byte[]	readAllBytes()	Reads all remaining bytes from the input stream for the current ZIP entry.
int	readNBytes(byte[] b, int off, int len)	Reads the requested number of bytes from the input stream into the given byte array for the current ZIP entry returning the number of inflated bytes.
byte[]	readNBytes(int len)	Reads up to a specified number of bytes from the input stream for the current ZIP entry.
long	skip(long n)	Skips over and discards n bytes of data from this input stream for the current ZIP entry.
void	skipNBytes(long n)	Skips over and discards exactly n bytes of data from this input stream for the current ZIP entry.
long	transferTo(OutputStream out)	Reads all bytes from this input stream for the current ZIP entry and writes the bytes to the given output stream in the order that they are read.

Methods declared in class java.util.zip.InflaterInputStream

fill, mark, markSupported, reset

Methods declared in class java.io.FilterInputStream

read

Methods declared in class java.io.InputStream

nullInputStream

Methods declared in class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

LOCSIG

static final long LOCSIG

Local file (LOC) header signature.

See Also:

• Constant Field Values

EXTSIG

static final long EXTSIG

Extra local (EXT) header signature.

See Also:

• Constant Field Values

CENSIG

static final long CENSIG

Central directory (CEN) header signature.

See Also:

• Constant Field Values

ENDSIG

static final long ENDSIG

End of central directory (END) header signature.

See Also:

• Constant Field Values

LOCHDR

static final int LOCHDR

Local file (LOC) header size in bytes (including signature).

See Also:

• Constant Field Values

EXTHDR

static final int EXTHDR

Extra local (EXT) header size in bytes (including signature).

See Also:

• Constant Field Values

CENHDR

static final int CENHDR

Central directory (CEN) header size in bytes (including signature).

See Also:

• Constant Field Values

ENDHDR

static final int ENDHDR

End of central directory (END) header size in bytes (including signature).

See Also:

• Constant Field Values

LOCVER

static final int LOCVER

Local file (LOC) header version needed to extract field offset.

See Also:

• Constant Field Values

LOCFLG

static final int LOCFLG

Local file (LOC) header general purpose bit flag field offset.

See Also:

• Constant Field Values

LOCHOW

static final int LOCHOW

Local file (LOC) header compression method field offset.

See Also:

• Constant Field Values

LOCTIM

static final int LOCTIM

Local file (LOC) header modification time field offset.

See Also:

• Constant Field Values

LOCCRC

static final int LOCCRC

Local file (LOC) header uncompressed file crc-32 value field offset.

See Also:

• Constant Field Values

LOCSIZ

static final int LOCSIZ

Local file (LOC) header compressed size field offset.

See Also:

• Constant Field Values

LOCLEN

static final int LOCLEN

Local file (LOC) header uncompressed size field offset.

See Also:

• Constant Field Values

LOCNAM

static final int LOCNAM

Local file (LOC) header filename length field offset.

See Also:

• Constant Field Values

LOCEXT

static final int LOCEXT

Local file (LOC) header extra field length field offset.

See Also:

• Constant Field Values

EXTCRC

static final int EXTCRC

Extra local (EXT) header uncompressed file crc-32 value field offset.

See Also:

• Constant Field Values

EXTSIZ

static final int EXTSIZ

Extra local (EXT) header compressed size field offset.

See Also:

• Constant Field Values

EXTLEN

static final int EXTLEN

Extra local (EXT) header uncompressed size field offset.

See Also:

• Constant Field Values

CENVEM

static final int CENVEM

Central directory (CEN) header version made by field offset.

See Also:

• Constant Field Values

CENVER

static final int CENVER

Central directory (CEN) header version needed to extract field offset.

See Also:

• Constant Field Values

CENFLG

static final int CENFLG

Central directory (CEN) header encrypt, decrypt flags field offset.

See Also:

• Constant Field Values

CENHOW

static final int CENHOW

Central directory (CEN) header compression method field offset.

See Also:

• Constant Field Values

CENTIM

static final int CENTIM

Central directory (CEN) header modification time field offset.

See Also:

• Constant Field Values

CENCRC

static final int CENCRC

Central directory (CEN) header uncompressed file crc-32 value field offset.

See Also:

• Constant Field Values

CENSIZ

static final int CENSIZ

Central directory (CEN) header compressed size field offset.

See Also:

• Constant Field Values

CENLEN

static final int CENLEN

Central directory (CEN) header uncompressed size field offset.

See Also:

• Constant Field Values

CENNAM

static final int CENNAM

Central directory (CEN) header filename length field offset.

See Also:

• Constant Field Values

CENEXT

static final int CENEXT

Central directory (CEN) header extra field length field offset.

See Also:

• Constant Field Values

CENCOM

static final int CENCOM

Central directory (CEN) header comment length field offset.

See Also:

• Constant Field Values

CENDSK

static final int CENDSK

Central directory (CEN) header disk number start field offset.

See Also:

• Constant Field Values

CENATT

static final int CENATT

Central directory (CEN) header internal file attributes field offset.

See Also:

• Constant Field Values

CENATX

static final int CENATX

Central directory (CEN) header external file attributes field offset.

See Also:

• Constant Field Values

CENOFF

static final int CENOFF

Central directory (CEN) header LOC header offset field offset.

See Also:

• Constant Field Values

ENDSUB

static final int ENDSUB

End of central directory (END) header number of entries on this disk field offset.

See Also:

• Constant Field Values

ENDTOT

static final int ENDTOT

End of central directory (END) header total number of entries field offset.

See Also:

• Constant Field Values

ENDSIZ

static final int ENDSIZ

End of central directory (END) header central directory size in bytes field offset.

See Also:

• Constant Field Values

ENDOFF

static final int ENDOFF

End of central directory (END) header offset for the first CEN header field offset.

See Also:

• Constant Field Values

ENDCOM

static final int ENDCOM

End of central directory (END) header ZIP file comment length field offset.

See Also:

• Constant Field Values

Constructor Details

ZipInputStream

public ZipInputStream(InputStream in)

Creates a new ZIP input stream.

The UTF-8 charset is used to decode the entry names.

Parameters:

in - the actual input stream

ZipInputStream

public ZipInputStream(InputStream in,
 Charset charset)

Creates a new ZIP input stream.

Parameters:

in - the actual input stream

charset - The charset to be used to decode the ZIP entry name (ignored if the language encoding bit of the ZIP entry's general purpose bit flag is set).

Since:

1.7

Method Details

getNextEntry

public ZipEntry getNextEntry()
                      throws IOException

Reads the next ZIP file entry and positions the stream at the beginning of the entry data.

Returns:

the next ZIP file entry, or null if there are no more entries

Throws:

ZipException - if a ZIP file error has occurred

IOException - if an I/O error has occurred

closeEntry

public void closeEntry()
                throws IOException

Closes the current ZIP entry and positions the stream for reading the next entry.

Throws:

ZipException - if a ZIP file error has occurred

IOException - if an I/O error has occurred

available

public int available()
              throws IOException

Returns 0 when end of stream is detected for the current ZIP entry or closeEntry() has been called on the current ZIP entry, otherwise returns 1.

Programs should not count on this method to return the actual number of bytes that could be read without blocking.

Overrides:

available in class InflaterInputStream

Returns:

0 when end of stream is detected for the current ZIP entry or closeEntry() has been called on the current ZIP entry, otherwise 1.

Throws:

IOException - if an I/O error occurs.

read

public int read()
         throws IOException

Reads the next byte of data from the input stream for the current ZIP entry. This method will block until enough input is available for decompression.

Overrides:

read in class InflaterInputStream

Returns:

the byte read, or -1 if the end of the stream is reached

Throws:

IOException - if an I/O error has occurred

See Also:

• FilterInputStream.in

readAllBytes

public byte[] readAllBytes()
                    throws IOException

Reads all remaining bytes from the input stream for the current ZIP entry. This method blocks until all remaining bytes have been read and end of stream is detected, or an exception is thrown. This method does not close the input stream.

When this stream reaches end of stream, further invocations of this method will return an empty byte array.

Note that this method is intended for simple cases where it is convenient to read all bytes into a byte array. It is not intended for reading input streams with large amounts of data.

If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes have been read. Consequently, the input stream may not be at end of stream and may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.

Overrides:

readAllBytes in class InputStream

Returns:

a byte array containing the bytes read from this input stream

Throws:

OutOfMemoryError - if an array of the required size cannot be allocated.

IOException - if an I/O error occurs

Since:

9

readNBytes

public byte[] readNBytes(int len)
                  throws IOException

Reads up to a specified number of bytes from the input stream for the current ZIP entry. This method blocks until the requested number of bytes has been read, end of stream is detected, or an exception is thrown. This method does not close the input stream.

The length of the returned array equals the number of bytes read from the stream. If len is zero, then no bytes are read and an empty byte array is returned. Otherwise, up to len bytes are read from the stream. Fewer than len bytes may be read if end of stream is encountered.

When this stream reaches end of stream, further invocations of this method will return an empty byte array.

Note that this method is intended for simple cases where it is convenient to read the specified number of bytes into a byte array. The total amount of memory allocated by this method is proportional to the number of bytes read from the stream which is bounded by len. Therefore, the method may be safely called with very large values of len provided sufficient memory is available.

If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes have been read. Consequently, the input stream may not be at end of stream and may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.

Overrides:

readNBytes in class InputStream

Implementation Note:

This method calls super.readNBytes(int len).

Parameters:

len - the maximum number of bytes to read

Returns:

a byte array containing the bytes read from this input stream

Throws:

OutOfMemoryError - if an array of the required size cannot be allocated.

IOException - if an I/O error occurs

Since:

11

readNBytes

public int readNBytes(byte[] b,
 int off,
 int len)
               throws IOException

Reads the requested number of bytes from the input stream into the given byte array for the current ZIP entry returning the number of inflated bytes. This method blocks until len bytes of input data have been read, end of stream is detected, or an exception is thrown. The number of bytes actually read, possibly zero, is returned. This method does not close the input stream.

In the case where end of stream is reached before len bytes have been read, then the actual number of bytes read will be returned. When this stream reaches end of stream, further invocations of this method will return zero.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read up to len bytes.

The first byte read is stored into element b[off], the next one in to b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k ] through b[off+len-1] unaffected.

If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes of b have been updated with data from the input stream. Consequently, the input stream and b may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.

Overrides:

readNBytes in class InputStream

Parameters:

b - the byte array into which the data is read

off - the start offset in b at which the data is written

len - the maximum number of bytes to read

Returns:

the actual number of bytes read into the buffer

Throws:

IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off

IOException - if an I/O error occurs

Since:

9

skipNBytes

public void skipNBytes(long n)
                throws IOException

Skips over and discards exactly n bytes of data from this input stream for the current ZIP entry. If n is zero, then no bytes are skipped. If n is negative, then no bytes are skipped. Subclasses may handle the negative value differently.

This method blocks until the requested number of bytes has been skipped, end of file is reached, or an exception is thrown.

If end of stream is reached before the stream is at the desired position, then an EOFException is thrown.

If an I/O error occurs, then the input stream may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.

Overrides:

skipNBytes in class InputStream

Parameters:

n - the number of bytes to be skipped.

Throws:

IOException - if the stream cannot be positioned properly or if an I/O error occurs.

Since:

12

See Also:

• InputStream.skip(long)

transferTo

public long transferTo(OutputStream out)
                throws IOException

Reads all bytes from this input stream for the current ZIP entry and writes the bytes to the given output stream in the order that they are read. On return, this input stream will be at end of stream. This method does not close either stream.

This method may block indefinitely reading from the input stream, or writing to the output stream. The behavior for the case where the input and/or output stream is asynchronously closed, or the thread interrupted during the transfer, is highly input and output stream specific, and therefore not specified.

If the total number of bytes transferred is greater than Long.MAX_VALUE, then Long.MAX_VALUE will be returned.

If an I/O error occurs reading from the input stream or writing to the output stream, then it may do so after some bytes have been read or written. Consequently, the input stream may not be at end of stream and one, or both, streams may be in an inconsistent state. It is strongly recommended that both streams be promptly closed if an I/O error occurs.

Overrides:

transferTo in class InputStream

Parameters:

out - the output stream, non-null

Returns:

the number of bytes transferred

Throws:

IOException - if an I/O error occurs when reading or writing

Since:

9

read

public int read(byte[] b,
 int off,
 int len)
         throws IOException

Reads the requested number of bytes from the input stream into the given byte array for the current ZIP entry returning the number of inflated bytes. If len is not zero, the method blocks until some input is available; otherwise, no bytes are read and 0 is returned.

If the current entry is compressed and this method returns a nonzero integer n then buf[off] through buf[off+n-1] contain the uncompressed data. The content of elements buf[off+n] through buf[off+len-1] is undefined, contrary to the specification of the InputStream superclass, so an implementation is free to modify these elements during the inflate operation. If this method returns -1 or throws an exception then the content of buf[off] through buf[off+len -1] is undefined.

Overrides:

read in class InflaterInputStream

Parameters:

b - the buffer into which the data is read

off - the start offset in the destination array b

len - the maximum number of bytes read

Returns:

the actual number of bytes read, or -1 if the end of the entry is reached

Throws:

IndexOutOfBoundsException - if off is negative, len is negative, or len is greater than b.length - off

ZipException - if a ZIP file error has occurred

IOException - if an I/O error has occurred

See Also:

• FilterInputStream.in

skip

public long skip(long n)
          throws IOException

Skips over and discards n bytes of data from this input stream for the current ZIP entry.

Overrides:

skip in class InflaterInputStream

Parameters:

n - the number of bytes to skip

Returns:

the actual number of bytes skipped

Throws:

ZipException - if a ZIP file error has occurred

IOException - if an I/O error has occurred

IllegalArgumentException - if n < 0

See Also:

• InputStream.skipNBytes(long)

close

public void close()
           throws IOException

Closes this input stream and releases any system resources associated with the stream.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class InflaterInputStream

Throws:

IOException - if an I/O error has occurred

See Also:

• FilterInputStream.in

createZipEntry

protected ZipEntry createZipEntry(String name)

Creates a new ZipEntry object for the specified entry name.

Parameters:

name - the ZIP file entry name

Returns:

the ZipEntry just created