A JAR is a ZIP
A JAR file is a way in Java to bundle classes together into one file. This is very useful for developing libraries of classes, which are related. Or for deploying Java application with one file, etc.

But sometimes we want to take a look inside a JAR file to see if everything you need is there. Or maybe we want to extract a specific file from the JAR file and store it somewhere else. We can use the JAR.EXE executable, which can be found in the java\bin folder: this is a simple command line tool, with all kind of parameter options, which make it a not so easy tool to use.

The internal structure of JAR file is the same as a normal ZIP file. Basically it is a ZIP file with a different extension (.jar), and that means we can use a program like WinZip to open a JAR file. This way it is much easier to extract files from a JAR file.