Where are the Java System Packages stored?

Question

I want to see all the java packages. Where are the packages stored in my machine? Can anyone help. I did search in jdk folder and found awt.dll and all. But its only a few. Can i see all of them?

Answer 1

If you want a list of packages in the standard installation, just go to the Javadocs and look in the upper left corner.

If you want to see the .class files, they're in lib\rt.jar in the JRE directory (.jar is the same as .zip, so you can open it with anything that can open zip files).

If you want to see the source code, look in src.zip in the JDK directory. If it's not there, you probably elected not to install it when you installed the JDK.

Keep in mind that packages are represented as folders on disk, so you might be a little disappointed by what you see.

Answer 2

From Java 9 onwards rt.jar was removed

The class and resource files previously stored in lib/rt.jar, lib/tools.jar, lib/dt.jar, and various other internal JAR files are now stored in a more efficient format in implementation-specific files in the lib directory. The format of these files is not specified and is subject to change without notice.

The System class files can now be accessed as shown below

FileSystem fs = FileSystems.getFileSystem(URI.create("jrt:/")); Path objClassFilePath = fs.getPath("modules", "java.base", "java/lang/Object.class");