Solved

Invoke other method than main(String[])

Posted on 2002-05-02
8
218 Views
Last Modified: 2010-03-31
Hi!
If I specify to a java program a class to run it runs its "public static void main(String[])" method.
Is there a way to run other "public static void methodName(String[])" method?
Thanks!
0
Comment
Question by:rzvika2
8 Comments
 
LVL 7

Expert Comment

by:tomboshell
ID: 6988005
Yes.  What is the problem?  What error are you getting?  You want to make another static method that is public and takes a string arrray as a parameter.  Should be no problem.  Just make sure that the static works on static variables and methods (or a constructor), otherwise you will get an error saying that you are trying to access a non-static something within a static method.  

Tom
0
 
LVL 5

Expert Comment

by:Jan Louwerens
ID: 6988018
No, you can't run anything besides main with the 'java' command. But you can do something like:

public class Test
{
   public static void main(String args[])
   {
      Test test = new Test();
      test.run();
   }

   public void run()
   {
      System.out.println("Running...");
   }
}

This way, you can call any public function of the class, static or not.
0
 
LVL 7

Expert Comment

by:tomboshell
ID: 6988047
Oh, to 'run' it.  Sorry, I misunderstood/misread the question.
0
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 35

Expert Comment

by:girionis
ID: 6988106
 As jlouwere pointed you cannot run any other method with the "java" command besides the "main" mehtd. But I am just curious. Why would you want to do it?
0
 
LVL 92

Expert Comment

by:objects
ID: 6988198
This is a duplicate question.
0
 
LVL 4

Accepted Solution

by:
Neutron earned 100 total points
ID: 6988214
hi rzvika2 :-)

I'm also curious about the purpose, anyway here is one way to do it using reflection:

-------8<-------cut here---------------------invoke.java-------
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

public class invoke
{
    public static void main( String[] args ) throws Throwable
    {
        if (args.length < 2)
        {
            System.out.println( "\nUSAGE: invoke <class> <method> {parameters}\n" );
            System.exit( 7 );
        }
       
        String className = args[0];
        String methodName = args[1];
       
        Class clazz = Class.forName( className );
       
        Method method = null;
        Class[] methodParameters = { args.getClass() };
       
        while (method==null && clazz!=null)
        {
            try
            {
                method = clazz.getDeclaredMethod( methodName, methodParameters );
            }
            catch( Throwable t )
            {
            }
           
            if (method != null)
            {
                if (!Modifier.isAbstract( method.getModifiers() ))
                {
                    if (Modifier.isPublic( method.getModifiers() ))
                    {
                        if (!Modifier.isStatic( method.getModifiers() ))
                        {
                            System.out.println( "Method "+methodName+" declared in the class "+clazz.getName()+" is not static." );
                            System.exit( 77 );
                        }
                    }
                    else
                    {
                        System.out.println( "Method "+methodName+" declared in the class "+clazz.getName()+" is not public." );
                        System.exit( 777 );
                    }
                }
                else
                {
                    System.out.println( "Method "+methodName+" declared in the class "+clazz.getName()+" is abstract." );
                    System.exit( 7777 );
                }
            }
           
            if (method == null)
            {
                if (clazz != Object.class)
                {
                    clazz = clazz.getSuperclass();
                }
                else
                {
                    clazz = null;
                }
            }
        } // while
       
        if (method != null)
        {
            int rest = args.length-2;
            String[] restArgs = new String[Math.max( rest, 0 )];
           
            if (rest > 0)
            {
                System.arraycopy( args, 2, restArgs, 0, rest );
            }
           
            method.invoke( null, new Object[]{ restArgs } );
        }
    }
   
} /* invoke */
-------8<-------cut here---------------------invoke.java-------

-------8<-------cut here---------------------example.java-------
public class example
{
    public static void subsidiary( String[] args )
    {
        System.out.println( "H, W!" );
       
        for (int i=0; i<args.length; i++)
        {
            System.out.println( args[i] );
        }
    }
   
} /* example */
-------8<-------cut here---------------------example.java-------

Hopefully this is what you had in mind.
To run this you can use following cmd-line:

java invoke example subsidiary 1 2 3 4 5 6 7

...which should behave just as if you ran

java example 1 2 3 4 5 6 7

...having 'subsidiary' as the default application method.

Best wishes,
    </ntr> :)
0
 

Author Comment

by:rzvika2
ID: 6990820
Thanks for the effort !
(By the way, I need it for supplying some methods (to enter the java program from command line) in a specific class that do different things).
0
 
LVL 4

Expert Comment

by:Neutron
ID: 6993175
No problem :)
I hope that the duplicate question objects mentioned didn't have a reply similar to mine. If so, I would be glad to share the points :-)

Greetings,
    </ntr> :)
0

Featured Post

On Demand Webinar - Networking for the Cloud Era

This webinar discusses:
-Common barriers companies experience when moving to the cloud
-How SD-WAN changes the way we look at networks
-Best practices customers should employ moving forward with cloud migration
-What happens behind the scenes of SteelConnect’s one-click button

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
configure dependency in POM for new database 3 43
String array comparison 4 45
eclipse console opening separately 2 35
program arguments vs VM arguments 4 25
Introduction Java can be integrated with native programs using an interface called JNI(Java Native Interface). Native programs are programs which can directly run on the processor. JNI is simply a naming and calling convention so that the JVM (Java…
Introduction This article is the last of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article covers our test design approach and then goes through a simple test case example, how …
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
This tutorial covers a practical example of lazy loading technique and early loading technique in a Singleton Design Pattern.

685 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question