For example, if a class file need to refer a class from package e.g. rt.jar stands for runtime and contains all of the compiled class files for the core Java Runtime environment.Ĥ) The rt.jar is where all the Java packages reside. It can also contain a manifest file, which can include Main-Class entry to make it an executable JAR, which can be run by using java -jar command.ġ. For those programmers, who are new to Java and not familiar with the JAR file, it is a zip like a file, precisely known as the Java archive which stores Java class files and any resource needed by the program. In this article, we will learn some interesting things about this magical JAR from the Java world. You should never be messing with rt.jar, it contains class files which is trusted by JVM and loaded without stringent security check it does for other class files.

Many developers think to include their classes inside rt.jar to solve classpath related problems, but that is a bad idea. From Java 7 release Apple has stopped distributing Java and if you separately install, it will have the same name as rt.jar. classes.jar, but that is only prior to JDK 1.7. In MacOSX it resides at a different location and also has a different name i.e. This file always resides inside the lib directory of JRE, at least in Windows and Linux. I have found that many Java programmer doesn't know what is rt.jar? and often confused with the role of rt.jar file or why we use of rt.jar file in Java? No surprise, the name is a little bit cryptic. Rt.jar stands for runtime JAR and contains the bootstrap classes, I mean all the classes from Core Java API.

Java jdk jre