[java] What is the use of rt.jar file in java?

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Why do we use rt.jar in a java project?

I am very confused to knowing about rt.jar file.

What is the role of rt.jar file or use of rt.jar file in java??

Thanks.

rt.jar contains all of the compiled class files for the base Java Runtime environment. You should not be messing with this jar file.

For MacOS it is called classes.jar and located under /System/Library/Frameworks/<java_version>/Classes . Same not messing with it rule applies there as well :).

http://javahowto.blogspot.com/2006/05/what-does-rtjar-stand-for-in.html

Your question is already answered here :

• Why do we use rt.jar file in java project ?

Basically, rt.jar contains all of the compiled class files for the base Java Runtime ("rt") Environment. Normally, javac should know the path to this file

Also, a good link on what happens if we try to include our class file in rt.jar.