Java : ZipOutputStream with Examples
July 15, 2023 
February 2, 2023
ZipOutputStream (Java SE 19 & JDK 19) API Examples.
You will find code examples on most ZipOutputStream methods.
Summary
This class implements an output stream filter for writing files in the ZIP file format. Includes support for both compressed and uncompressed entries.
// --------
// Compression
try (final var zos = new ZipOutputStream(Files.newOutputStream(path))) {
zos.putNextEntry(new ZipEntry("bbb.txt"));
zos.write("YYYYY".getBytes());
zos.putNextEntry(new ZipEntry("ccc.txt"));
zos.write("ZZZZZ".getBytes());
}
// --- PowerShell ---
//PS R:\java-work> ls -name
//aaa.zip
//
//PS R:\java-work> Expand-Archive .\aaa.zip .
//PS R:\java-work> ls -name
//aaa.zip
//bbb.txt
//ccc.txt
//
//PS R:\java-work> cat .\bbb.txt
//YYYYY
//PS R:\java-work> cat .\ccc.txt
//ZZZZZ
// --------
// Decompression
try (final var zis = new ZipInputStream(Files.newInputStream(path))) {
final var entry1 = zis.getNextEntry();
if (entry1 != null) {
System.out.println(entry1.getName()); // bbb.txt
final var uncompressed = zis.readAllBytes();
System.out.println(Arrays.toString(uncompressed)); // [89, 89, 89, 89, 89]
System.out.println(new String(uncompressed)); // YYYYY
}
final var entry2 = zis.getNextEntry();
if (entry2 != null) {
System.out.println(entry2.getName()); // ccc.txt
final var uncompressed = zis.readAllBytes();
System.out.println(Arrays.toString(uncompressed)); // [90, 90, 90, 90, 90]
System.out.println(new String(uncompressed)); // ZZZZZ
}
System.out.println(zis.getNextEntry()); // null
}
Fields
static final int CENATT
Central directory (CEN) header internal file attributes field offset.
System.out.println(ZipOutputStream.CENATT); // 36
static final int CENATX
Central directory (CEN) header external file attributes field offset.
System.out.println(ZipOutputStream.CENATX); // 38
static final int CENCOM
Central directory (CEN) header comment length field offset.
System.out.println(ZipOutputStream.CENCOM); // 32
static final int CENCRC
Central directory (CEN) header uncompressed file crc-32 value field offset.
System.out.println(ZipOutputStream.CENCRC); // 16
static final int CENDSK
Central directory (CEN) header disk number start field offset.
System.out.println(ZipOutputStream.CENDSK); // 34
static final int CENEXT
Central directory (CEN) header extra field length field offset.
System.out.println(ZipOutputStream.CENEXT); // 30
static final int CENFLG
Central directory (CEN) header encrypt, decrypt flags field offset.
System.out.println(ZipOutputStream.CENFLG); // 8
static final int CENHDR
Central directory (CEN) header size in bytes (including signature).
System.out.println(ZipOutputStream.CENHDR); // 46
static final int CENHOW
Central directory (CEN) header compression method field offset.
System.out.println(ZipOutputStream.CENHOW); // 10
static final int CENLEN
Central directory (CEN) header uncompressed size field offset.
System.out.println(ZipOutputStream.CENLEN); // 24
static final int CENNAM
Central directory (CEN) header filename length field offset.
System.out.println(ZipOutputStream.CENNAM); // 28
static final int CENOFF
Central directory (CEN) header LOC header offset field offset.
System.out.println(ZipOutputStream.CENOFF); // 42
static final long CENSIG
Central directory (CEN) header signature.
System.out.printf("%#x", ZipOutputStream.CENSIG); // 0x2014b50
static final int CENSIZ
Central directory (CEN) header compressed size field offset.
System.out.println(ZipOutputStream.CENSIZ); // 20
static final int CENTIM
Central directory (CEN) header modification time field offset.
System.out.println(ZipOutputStream.CENTIM); // 12
static final int CENVEM
Central directory (CEN) header version made by field offset.
System.out.println(ZipOutputStream.CENVEM); // 4
static final int CENVER
Central directory (CEN) header version needed to extract field offset.
System.out.println(ZipOutputStream.CENVER); // 6
static final int DEFLATED
Compression method for compressed (DEFLATED) entries.
System.out.println(ZipOutputStream.DEFLATED); // 8
static final int ENDCOM
End of central directory (END) header zip file comment length field offset.
System.out.println(ZipOutputStream.ENDCOM); // 20
static final int ENDHDR
End of central directory (END) header size in bytes (including signature).
System.out.println(ZipOutputStream.ENDHDR); // 22
static final int ENDOFF
End of central directory (END) header offset for the first CEN header field offset.
System.out.println(ZipOutputStream.ENDOFF); // 16
static final long ENDSIG
End of central directory (END) header signature.
System.out.printf("%#x", ZipOutputStream.ENDSIG); // 0x6054b50
static final int ENDSIZ
End of central directory (END) header central directory size in bytes field offset.
System.out.println(ZipOutputStream.ENDSIZ); // 12
static final int ENDSUB
End of central directory (END) header number of entries on this disk field offset.
System.out.println(ZipOutputStream.ENDSUB); // 8
static final int ENDTOT
End of central directory (END) header total number of entries field offset.
System.out.println(ZipOutputStream.ENDTOT); // 10
static final int EXTCRC
Extra local (EXT) header uncompressed file crc-32 value field offset.
System.out.println(ZipOutputStream.EXTCRC); // 4
static final int EXTHDR
Extra local (EXT) header size in bytes (including signature).
System.out.println(ZipOutputStream.EXTHDR); // 16
static final int EXTLEN
Extra local (EXT) header uncompressed size field offset.
System.out.println(ZipOutputStream.EXTLEN); // 12
static final long EXTSIG
Extra local (EXT) header signature.
System.out.printf("%#x", ZipOutputStream.EXTSIG); // 0x8074b50
static final int EXTSIZ
Extra local (EXT) header compressed size field offset.
System.out.println(ZipOutputStream.EXTSIZ); // 8
static final int LOCCRC
Local file (LOC) header uncompressed file crc-32 value field offset.
System.out.println(ZipOutputStream.LOCCRC); // 14
static final int LOCEXT
Local file (LOC) header extra field length field offset.
System.out.println(ZipOutputStream.LOCEXT); // 28
static final int LOCFLG
Local file (LOC) header general purpose bit flag field offset.
System.out.println(ZipOutputStream.LOCFLG); // 6
static final int LOCHDR
Local file (LOC) header size in bytes (including signature).
System.out.println(ZipOutputStream.LOCHDR); // 30
static final int LOCHOW
Local file (LOC) header compression method field offset.
System.out.println(ZipOutputStream.LOCHOW); // 8
static final int LOCLEN
Local file (LOC) header uncompressed size field offset.
System.out.println(ZipOutputStream.LOCLEN); // 22
static final int LOCNAM
Local file (LOC) header filename length field offset.
System.out.println(ZipOutputStream.LOCNAM); // 26
static final long LOCSIG
Local file (LOC) header signature.
System.out.printf("%#x", ZipOutputStream.LOCSIG); // 0x4034b50
static final int LOCSIZ
Local file (LOC) header compressed size field offset.
System.out.println(ZipOutputStream.LOCSIZ); // 18
static final int LOCTIM
Local file (LOC) header modification time field offset.
System.out.println(ZipOutputStream.LOCTIM); // 10
static final int LOCVER
Local file (LOC) header version needed to extract field offset.
System.out.println(ZipOutputStream.LOCVER); // 4
static final int STORED
Compression method for uncompressed (STORED) entries.
System.out.println(ZipOutputStream.STORED); // 0
Fields declared in DeflaterOutputStream
Fields declared in FilterOutputStream
Constructors
ZipOutputStream (OutputStream out)
Creates a new ZIP output stream.
final var input = "aaaaa".getBytes();
// [97, 97, 97, 97, 97]
System.out.println(Arrays.toString(input));
final var out = new ByteArrayOutputStream();
try (final var zos = new ZipOutputStream(out)) {
zos.putNextEntry(new ZipEntry("aaa.txt"));
zos.write(input);
}
final var compressed = out.toByteArray();
System.out.println(compressed.length); // 133
// [80, 75, 3, 4, 20, 0, 8, 8, 8, 0, -106, -118, 63, 86, 0, 0, 0, 0, ...]
System.out.println(Arrays.toString(compressed));
ZipOutputStream (OutputStream out, Charset charset)
Creates a new ZIP output stream.
Please see ZipOutputStream(OutputStream out) for out parameter.
final var charset = Charset.forName("Shift_JIS");
final var out = new ByteArrayOutputStream();
try (final var zos = new ZipOutputStream(out, charset)) {
zos.putNextEntry(new ZipEntry("aaa.txt"));
zos.putNextEntry(new ZipEntry("○△×.txt"));
}
final var compressed = out.toByteArray();
System.out.println(compressed.length); // 244
try (final var zis = new ZipInputStream(new ByteArrayInputStream(compressed), charset)) {
final var entry1 = zis.getNextEntry();
if (entry1 != null) {
System.out.println(entry1.getName()); // aaa.txt
}
final var entry2 = zis.getNextEntry();
if (entry2 != null) {
System.out.println(entry2.getName()); // ○△×.txt
}
}
Methods
void close ()
Closes the ZIP output stream as well as the stream being filtered.
final var file = Path.of("R:", "java-work", "aaa.zip");
System.out.println(file); // R:\java-work\aaa.zip
try (final var zos = new ZipOutputStream(Files.newOutputStream(file))) {
zos.putNextEntry(new ZipEntry("xxx.txt"));
zos.write("aaaaa".getBytes());
}
final var bytes = Files.readAllBytes(file);
System.out.println(bytes.length); // 133
An example without try-with-resources.
final var file = Path.of("R:", "java-work", "aaa.zip");
System.out.println(file); // R:\java-work\aaa.zip
final var zos = new ZipOutputStream(Files.newOutputStream(file));
try {
zos.putNextEntry(new ZipEntry("xxx.txt"));
zos.write("aaaaa".getBytes());
} finally {
zos.close();
}
final var bytes = Files.readAllBytes(file);
System.out.println(bytes.length); // 133
void closeEntry ()
Closes the current ZIP entry and positions the stream for writing the next entry.
final var input = "aaaaaaaaaa".getBytes();
// [97, 97, 97, 97, 97, 97, 97, 97, 97, 97]
System.out.println(Arrays.toString(input));
final var out = new ByteArrayOutputStream();
try (final var zos = new ZipOutputStream(out)) {
final var entry = new ZipEntry("aaa.txt");
zos.putNextEntry(entry);
zos.write(input);
System.out.println(entry.getSize()); // -1
System.out.println(entry.getCompressedSize()); // -1
System.out.println(out.toByteArray().length); // 37
zos.closeEntry();
System.out.println(entry.getSize()); // 10
System.out.println(entry.getCompressedSize()); // 5
System.out.println(out.toByteArray().length); // 58
}
final var compressed = out.toByteArray();
System.out.println(compressed.length); // 133
void finish ()
Finishes writing the contents of the ZIP output stream without closing the underlying stream.
final var input = "aaaaa".getBytes();
// [97, 97, 97, 97, 97]
System.out.println(Arrays.toString(input));
final var out = new ByteArrayOutputStream();
try (final var zos = new ZipOutputStream(out)) {
zos.putNextEntry(new ZipEntry("aaa.txt"));
zos.write(input);
zos.finish();
// [80, 75, 3, 4, 20, 0, 8, 8, 8, 0, 59, -102, 63, 86, 0, 0, 0, ...]
System.out.println(Arrays.toString(out.toByteArray()));
// The stream is not closed.
out.write(1);
out.write(2);
out.write(3);
}
final var compressed = out.toByteArray();
// [80, 75, 3, 4, 20, 0, 8, 8, 8, 0, 59, -102, 63, 86, 0, 0, 0, ..., 1, 2, 3]
System.out.println(Arrays.toString(compressed));
void putNextEntry (ZipEntry e)
Begins writing a new ZIP file entry and positions the stream to the start of the entry data.
final var path = Path.of("R:", "java-work", "aaa.zip");
System.out.println(path); // R:\java-work\aaa.zip
// --------
// Compression
try (final var zos = new ZipOutputStream(Files.newOutputStream(path))) {
zos.putNextEntry(new ZipEntry("bbb.txt"));
zos.write("YYYYY".getBytes());
zos.putNextEntry(new ZipEntry("ccc.txt"));
zos.write("ZZZZZ".getBytes());
}
// --------
// Decompression
try (final var zis = new ZipInputStream(Files.newInputStream(path))) {
final var entry1 = zis.getNextEntry();
if (entry1 != null) {
System.out.println(entry1.getName()); // bbb.txt
final var uncompressed = zis.readAllBytes();
System.out.println(Arrays.toString(uncompressed)); // [89, 89, 89, 89, 89]
System.out.println(new String(uncompressed)); // YYYYY
}
final var entry2 = zis.getNextEntry();
if (entry2 != null) {
System.out.println(entry2.getName()); // ccc.txt
final var uncompressed = zis.readAllBytes();
System.out.println(Arrays.toString(uncompressed)); // [90, 90, 90, 90, 90]
System.out.println(new String(uncompressed)); // ZZZZZ
}
System.out.println(zis.getNextEntry()); // null
}
void setComment (String comment)
Sets the ZIP file comment.
final var path = Path.of("R:", "java-work", "aaa.zip");
System.out.println(path); // R:\java-work\aaa.zip
try (final var zos = new ZipOutputStream(Files.newOutputStream(path))) {
zos.setComment("Comment!");
zos.putNextEntry(new ZipEntry("bbb.txt"));
zos.write("YYYYY".getBytes());
}
try (final var zipFile = new ZipFile(path.toFile())) {
System.out.println(zipFile.getComment()); // Comment!
}
void setLevel (int level)
Sets the compression level for subsequent entries which are DEFLATED.
final var input = "aaaaaaaaaa".getBytes();
System.out.println(input.length); // 10
final var out = new ByteArrayOutputStream();
try (final var zos = new ZipOutputStream(out)) {
final var entry1 = new ZipEntry("aaa.txt");
zos.putNextEntry(entry1);
zos.setLevel(Deflater.BEST_COMPRESSION);
zos.write(input);
zos.closeEntry();
System.out.println(entry1.getCompressedSize()); // 5
final var entry2 = new ZipEntry("bbb.txt");
zos.putNextEntry(entry2);
zos.setLevel(Deflater.NO_COMPRESSION);
zos.write(input);
zos.closeEntry();
System.out.println(entry2.getCompressedSize()); // 15
}
System.out.println(out.toByteArray().length); // 254
void setMethod (int method)
Sets the default compression method for subsequent entries.
final var out = new ByteArrayOutputStream();
try (final var zos = new ZipOutputStream(out)) {
zos.setMethod(ZipEntry.STORED);
final var input = "aaaaaaaaaa".getBytes();
System.out.println(input.length); // 10
final var crc = new CRC32();
crc.update(input);
final var entry = new ZipEntry("aaa.txt");
entry.setCrc(crc.getValue());
entry.setSize(input.length);
zos.putNextEntry(entry);
zos.write(input);
}
System.out.println(out.toByteArray().length); // 122
void write (byte[] b, int off, int len)
Writes an array of bytes to the current ZIP entry data.
final byte[] input = {10, 20, 30, 40, 50};
System.out.println(Arrays.toString(input)); // [10, 20, 30, 40, 50]
{
final var out = new ByteArrayOutputStream();
try (final var zos = new ZipOutputStream(out)) {
zos.putNextEntry(new ZipEntry("aaa.txt"));
zos.write(input, 0, 5);
}
final var compressed = out.toByteArray();
System.out.println(compressed.length); // 135
try (final var zis = new ZipInputStream(new ByteArrayInputStream(compressed))) {
final var entry = zis.getNextEntry();
if (entry != null) {
final var uncompressed = zis.readAllBytes();
// [10, 20, 30, 40, 50]
System.out.println(Arrays.toString(uncompressed));
}
}
}
{
final var out = new ByteArrayOutputStream();
try (final var zos = new ZipOutputStream(out)) {
zos.putNextEntry(new ZipEntry("aaa.txt"));
zos.write(input, 1, 3);
}
final var compressed = out.toByteArray();
System.out.println(compressed.length); // 133
try (final var zis = new ZipInputStream(new ByteArrayInputStream(compressed))) {
final var entry = zis.getNextEntry();
if (entry != null) {
final var uncompressed = zis.readAllBytes();
// [20, 30, 40]
System.out.println(Arrays.toString(uncompressed));
}
}
}