Re: help: a reflection question

From:

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 18 Feb 2011 13:10:05 -0500

Message-ID:

<4d5eb5fc$0$23752$14726298@news.sunsite.dk>

On 18-02-2011 11:41, www wrote:

I have the following code in testing code(MyTest.java) to run several
potential programs. There are ProgramsA.java, ProgramB.java,
ProgramC.java and they all have main() method. But they don't share
same parent class.

public void runProgram(String programName)
{
         final Class<?> myClass = Class.forName(programName);
         final Object myObj = myClass.newInstance();

         myObj.main(); //OOPS, error!

Try:

Class declarg[] = new Class[1];
declarg[0] = String[].class;
Method m = Class.forName(programClassName).getMethod("main", declarg);
Object callarg[] = new Object[1];
callarg[0] = new String[0];
m.invoke(null, callarg);

//this works:
        if(programName.equalsIgnoreCase("ProgramA")) {
              ((ProgramA).myObj).main();
        }
        else if(programName.equalsIgnoreCase("ProgramB")) {
              ((ProgramB).myObj).main();
        }
        else{
              ((ProgramC).myObj).main();
        }
}
//BUT, MyTest.java has import statements at the top:
import ProgramA;
import ProgramB;
import ProgramC;

The problem is that if I want to wrap MyTest.class into a JAR file to
give to somebody who is interested in using MyTest.class to test his
ProgramW.java which has nothing to do with ProgramA, B or C, I also
need to include ProgramA.class, ProgramB.class and ProgramC.class into
the JAR file. Plus, the code above won't work with ProgramW.java.

I understand polymorphism to have an interface Program.java for all
the programs. But I am wondering if reflection can achieve it without
a sharing interface.

Yes.

See above.

Arne