CODEWITHSUNDEEP
java
ryantm
ryantm

Reputation: 8417

$0 (Program Name) in Java? Discover main class?

Is there a way to find the name of the program that is running in Java? The class of the main method would be good enough.

Upvotes: 54

Views: 29158

Answers (8)

John Meagher
John Meagher

Reputation: 24698

To expand on @jodonnell you can also get all stack traces in the system using Thread.getAllStackTraces(). From this you can search all the stack traces for the main Thread to determine what the main class is. This will work even if your class is not running in the main thread.

Upvotes: 15

Nadav Brandes
Nadav Brandes

Reputation: 191

System.getProperty("sun.java.command")

Upvotes: 18

Andrew Taylor
Andrew Taylor

Reputation: 1398

This is the code I came up with when using the combined responses of jodonnell and John Meagher. It stores the main class in a static variable to reduce overhead of repeated calls:

private static Class<?> mainClass;

public static Class<?> getMainClass() {
  if (mainClass != null)
    return mainClass;

  Collection<StackTraceElement[]> stacks = Thread.getAllStackTraces().values();
  for (StackTraceElement[] currStack : stacks) {
    if (currStack.length==0)
      continue;
    StackTraceElement lastElem = currStack[currStack.length - 1];
    if (lastElem.getMethodName().equals("main")) {
      try {
        String mainClassName = lastElem.getClassName();
        mainClass = Class.forName(mainClassName);
        return mainClass;
      } catch (ClassNotFoundException e) {
        // bad class name in line containing main?! 
        // shouldn't happen
        e.printStackTrace();
      }
    }
  }
  return null;
}

Upvotes: 8

tschodt
tschodt

Reputation: 164

For access to the class objects when you are in a static context

public final class ClassUtils {
    public static final Class[] getClassContext() {
        return new SecurityManager() { 
            protected Class[] getClassContext(){return super.getClassContext();}
        }.getClassContext(); 
    };
    private ClassUtils() {};
    public static final Class getMyClass() { return getClassContext()[2];}
    public static final Class getCallingClass() { return getClassContext()[3];}
    public static final Class getMainClass() { 
        Class[] c = getClassContext();
        return c[c.length-1];
    }
    public static final void main(final String[] arg) {
        System.out.println(getMyClass());
        System.out.println(getCallingClass());
        System.out.println(getMainClass());
    }
}

Obviously here all 3 calls will return 

class ClassUtils

but you get the picture;

classcontext[0] is the securitymanager
classcontext[1] is the anonymous securitymanager
classcontext[2] is the class with this funky getclasscontext method
classcontext[3] is the calling class
classcontext[last entry] is the root class of this thread.

Upvotes: 2

color
color

Reputation: 1

Try this :

Java classes have static instance of their own class (java.lang.Class type).

That means if we have a class named Main. Then we can get its class instance by Main.class

If you're interested in name only then,

String className = Main.class.getName();

Upvotes: -3

Adam
Adam

Reputation: 1

Or you could just use getClass(). You can do something like:

public class Foo
{
    public static final String PROGNAME = new Foo().getClass().getName();
}

And then PROGNAME will be available anywhere inside Foo. If you're not in a static context, it gets easier as you could use this:

String myProgramName = this.getClass().getName();

Upvotes: -5

jodonnell
jodonnell

Reputation: 50437

Try this:

    StackTraceElement[] stack = Thread.currentThread ().getStackTrace ();
    StackTraceElement main = stack[stack.length - 1];
    String mainClass = main.getClassName ();

Of course, this only works if you're running from the main thread. Unfortunately I don't think there's a system property you can query to find this out.

Edit: Pulling in @John Meagher's comment, which is a great idea:

To expand on @jodonnell you can also get all stack traces in the system using Thread.getAllStackTraces(). From this you can search all the stack traces for the "main" Thread to determine what the main class is. This will work even if your class is not running in the main thread.

Upvotes: 45

polarbear
polarbear

Reputation: 12935

Also from the command line you could run the jps tool. Sounds like a 

jps -l

will get you what you want.

Upvotes: 4

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