how to set default main class in java?

I have 2 classes within same package. Both classes have main method in them. Now I want to build a jar file. I want to build 2 jar files which use different main functions as default main.

eg

class A
{
  public static void main(String args[])
  {
    //do something
  }
}

class B
{
  public static void main(String args[])
  {
    //do something
  }
}

How do I do it in NetBeans IDE?

I found the answer. U can do it easily in netbeans: 1)right click on project >properties > run > select the class frm and drop down list. So simple in netbeans. Netbeans rocks!