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/OpenJDK 21

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.

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

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

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:

EXTSIG

static final long EXTSIG
Extra local (EXT) header signature.
See Also:

CENSIG

static final long CENSIG
Central directory (CEN) header signature.
See Also:

ENDSIG

static final long ENDSIG
End of central directory (END) header signature.
See Also:

LOCHDR

static final int LOCHDR
Local file (LOC) header size in bytes (including signature).
See Also:

EXTHDR

static final int EXTHDR
Extra local (EXT) header size in bytes (including signature).
See Also:

CENHDR

static final int CENHDR
Central directory (CEN) header size in bytes (including signature).
See Also:

ENDHDR

static final int ENDHDR
End of central directory (END) header size in bytes (including signature).
See Also:

LOCVER

static final int LOCVER
Local file (LOC) header version needed to extract field offset.
See Also:

LOCFLG

static final int LOCFLG
Local file (LOC) header general purpose bit flag field offset.
See Also:

LOCHOW

static final int LOCHOW
Local file (LOC) header compression method field offset.
See Also:

LOCTIM

static final int LOCTIM
Local file (LOC) header modification time field offset.
See Also:

LOCCRC

static final int LOCCRC
Local file (LOC) header uncompressed file crc-32 value field offset.
See Also:

LOCSIZ

static final int LOCSIZ
Local file (LOC) header compressed size field offset.
See Also:

LOCLEN

static final int LOCLEN
Local file (LOC) header uncompressed size field offset.
See Also:

LOCNAM

static final int LOCNAM
Local file (LOC) header filename length field offset.
See Also:

LOCEXT

static final int LOCEXT
Local file (LOC) header extra field length field offset.
See Also:

EXTCRC

static final int EXTCRC
Extra local (EXT) header uncompressed file crc-32 value field offset.
See Also:

EXTSIZ

static final int EXTSIZ
Extra local (EXT) header compressed size field offset.
See Also:

EXTLEN

static final int EXTLEN
Extra local (EXT) header uncompressed size field offset.
See Also:

CENVEM

static final int CENVEM
Central directory (CEN) header version made by field offset.
See Also:

CENVER

static final int CENVER
Central directory (CEN) header version needed to extract field offset.
See Also:

CENFLG

static final int CENFLG
Central directory (CEN) header encrypt, decrypt flags field offset.
See Also:

CENHOW

static final int CENHOW
Central directory (CEN) header compression method field offset.
See Also:

CENTIM

static final int CENTIM
Central directory (CEN) header modification time field offset.
See Also:

CENCRC

static final int CENCRC
Central directory (CEN) header uncompressed file crc-32 value field offset.
See Also:

CENSIZ

static final int CENSIZ
Central directory (CEN) header compressed size field offset.
See Also:

CENLEN

static final int CENLEN
Central directory (CEN) header uncompressed size field offset.
See Also:

CENNAM

static final int CENNAM
Central directory (CEN) header filename length field offset.
See Also:

CENEXT

static final int CENEXT
Central directory (CEN) header extra field length field offset.
See Also:

CENCOM

static final int CENCOM
Central directory (CEN) header comment length field offset.
See Also:

CENDSK

static final int CENDSK
Central directory (CEN) header disk number start field offset.
See Also:

CENATT

static final int CENATT
Central directory (CEN) header internal file attributes field offset.
See Also:

CENATX

static final int CENATX
Central directory (CEN) header external file attributes field offset.
See Also:

CENOFF

static final int CENOFF
Central directory (CEN) header LOC header offset field offset.
See Also:

ENDSUB

static final int ENDSUB
End of central directory (END) header number of entries on this disk field offset.
See Also:

ENDTOT

static final int ENDTOT
End of central directory (END) header total number of entries field offset.
See Also:

ENDSIZ

static final int ENDSIZ
End of central directory (END) header central directory size in bytes field offset.
See Also:

ENDOFF

static final int ENDOFF
End of central directory (END) header offset for the first CEN header field offset.
See Also:

ENDCOM

static final int ENDCOM
End of central directory (END) header zip file comment length field offset.
See Also:

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:

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:
NullPointerException - if b is null
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:

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:
NullPointerException - if out is null
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:
NullPointerException - if b is null.
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:

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:

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:

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

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/zip/ZipInputStream.html