So you got a JAR file which contains your favorite Java game and you are
wondering How to run Java program from JAR file? Or you may be simply trying your hand after
running
Java program from command prompt and Eclipse IDE. Anyway its good to know
How to execute Java program from JAR file, as JAR file is most popular way of
shipping Java programs. JAR file usually contains all source and resource in
form of class files, images, sound files etc. In order to run Java program from
JAR file, it must be an executable
JAR file i.e. it manifest file inside META-INF folder
must contain a Main-class entry like Main-Class:
Hello, which specify name of Java class which contains standard main
method in Java. Without Main-class entry you
can not run a JAR file in Java and if you try to run such jar file using jar command
you will get error "Failed to load Main-Class manifest attribute
from HelloWorld.jar". If you are not very much familiar with JAR file
and don't know How to create an executable JAR, See this step by step tutorial on
How
to create executable JAR in Java. In this tutorial we will only focusing on
running Java program from an executable JAR file.
Running Java program from JAR file in Java
Suppose we have hello.jar which contains Hello.java class
which has main
method as entry point. When we run this JAR file using JAR command, JVM
will call this main method which is specified in its manifest file as shown
below :
Manifest-version: 1.0
Main-Class: Hello
By the way don't forget to set
PATH and Classpath in Java before
running Java program. If classpath is specified in manifest file than that will
be used by JVM and it will ignore CLASSPATH environment variable, If you are
not familiar with these details then see How
classpath works in Java, must read for any beginner in Java. Once you are
sure that Java is installed in your machine, path and classpath are proper,
just execute following command and it will run your Java program from JAR file
itself :
java -jar Hello.jar
If you face any issue related to Java, classpath and path while running
your Java program from JAR file, please post here.
Other Java programming tutorial you may find useful
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