JAR File - What It Is & How to Open One #
A JAR (Java ARchive) file is a package file format, based on the ZIP file format, used to aggregate many Java class files, metadata and resources (text, images, etc.) into one file for distribution.1
The contents of a JAR file can be extracted using any standard decompression tool, or the
jar command line utility.
unzip -d foo foo.jar
-d <dir>: extract files into dir.
jar -xf foo.jar
-x: extract named (or all) files from archive.
-f <file>: specify archive file name.
Decompile Class Files #
Java class files are compiled files containing Java bytecode that can be executed by a Java Virtual Machine (JVM). To decompile and view the source code in plain text any Java decompiler can be used. JAD was the go-to for many years but only supports Java 1.4 or below. The Java-Decompiler Project, Procyon, and online tools like DevToolZone’s Java Decompiler are good alternatives.
“JAR File Specification.” JAVA SE Documentation, https://docs.oracle.com/javase/6/docs/technotes/guides/jar/jar.html#JARIndex. ↩︎