CODEWITHSUNDEEP
javajavac
ren
ren

Reputation: 3993

java: find a class with main method automatically

Is there a way to tell jvm to look for a class with entry main method automatically rather than to specify it when invoking java ClassWithMainMethod?

In other words, I have directory with many compiled classes one of which has main method and I want to only specify that directory.

Upvotes: 2

Views: 3276

Answers (4)

millimoose
millimoose

Reputation: 39990

If, in your scenario:

  • it is okay to execute the first classfile in a directory;
  • the classes in this directory are in the default package;
  • the javap command is available – i.e. you've got a JDK installed, not just a JRE;

you could use the following bash script:

#!/usr/bin/env sh
for classfile in *.class; do
    classname=$(echo $classfile | cut -f 1 -d '.')
    echo $classname
    if javap -public $classname | fgrep 'public static void main(java.lang.String[])'; then
        java $classname "$@"
    fi
done

Upvotes: 7

dinesh028
dinesh028

Reputation: 2187

If there are more then one class with main method?

I think you can create a executable Jar file and specify class having main function in manifest file. So, whenever user will run jar file. Class with main function will be executed.

Upvotes: 0

Óscar López
Óscar López

Reputation: 236170

If your application is inside a .jar file, you can specify the main class in its manifest

Upvotes: 0

JB Nizet
JB Nizet

Reputation: 692231

No, there is no way to do that. You can create an executable jar, and define what the main class is in the jar manifest, allowing you to use 

java -jar MyJar.jar

though.

See http://docs.oracle.com/javase/tutorial/deployment/jar/appman.html

You may also deliver your app with a script which executes the appropriate command for you:

#startup.cmd
java -cp ... com.foo.bar.Main

Upvotes: 5

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