The Apache Commons Compress library defines an API for working with ar, cpio, Unix dump, tar, zip, gzip, XZ, Pack200, bzip2, 7z, arj, lzma, snappy, DEFLATE, lz4, Brotli, Zstandard, DEFLATE64 and Z files.

The code in this component has many origins:

• The bzip2, tar and zip support came from Avalon's Excalibur, but originally from Ant, as far as life in Apache goes. The tar package is originally Tim Endres' public domain package. The bzip2 package is based on the work done by Keiron Liddle as well as Julian Seward's libbzip2. It has migrated via:
  Ant -> Avalon-Excalibur -> Commons-IO -> Commons-Compress.
• The cpio package has been contributed by Michael Kuss and the jRPM project.

The current release is 1.18 and requires Java 7.

Below we highlight some new features, for a full list of changes see the Changes Report.

The compress component is split into compressors and archivers. While compressors (un)compress streams that usually store a single entry, archivers deal with archives that contain structured content represented by ArchiveEntry instances which in turn usually correspond to single files or directories.

Currently the bzip2, Pack200, XZ, gzip, lzma, brotli, Zstandard and Z formats are supported as compressors where gzip support is mostly provided by the java.util.zip package and Pack200 support by the java.util.jar package of the Java class library. XZ and lzma support is provided by the public domain XZ for Java library. Brotli support is provided by the MIT licensed Google Brotli decoder. Zstandard support is provided by the BSD licensed Zstd-jni. As of Commons Compress 1.18 support for the DEFLATE64, Z and Brotli formats is read-only.

The ar, arj, cpio, dump, tar, 7z and zip formats are supported as archivers where the zip implementation provides capabilities that go beyond the features found in java.util.zip. As of Commons Compress 1.18 support for the dump and arj formats is read-only - 7z can read most compressed and encrypted archives but only write unencrypted ones. LZMA(2) support in 7z requires XZ for Java as well.

The compress component provides abstract base classes for compressors and archivers together with factories that can be used to choose implementations by algorithm name. In the case of input streams the factories can also be used to guess the format and provide the matching implementation.

• The user guide contains more detailed information and some examples.
• The known limitations and problems page lists the currently known problems grouped by the format they apply to.
• The Javadoc of the latest GIT
• The GIT repository can be browsed.

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