How to use java.lang.Class.getMethod() and java.lang.reflect.Method.invoke(

Question

I want to call a specified method of one class dynamically. I use the method
"getMethod()" in package "java.lang.Class" to get method and "invoke()" in
" java.lang.reflect.Method " to invoke method.
The problem is as following :
1. There are two argument in this method "getMethod(String MethodName , Class[] paremterTypes)" in package "Class". I have no idea about the second parameter " Class[] parameterTypes ".what does the argument exactly mean ?
2. There are two argument in the method "invoke(object obj, object[] obj)" in package "Method".
I have no idea about the second parameter "object[] obj ".what is mean ?
I pass " null " value to it and it works.But i pass anothers ,jvm will throw exception.

Answer 1

I have a generic Method Executer that has a method like
public Object execute(String className, String methodName, Object args)
    String fullClassName = packageName + className ;
    Class delegateClass = Class.forName(fullClassName);
    BaseDelegate delegate = (BaseDelegate)delegateClass.newInstance();
    Method method = null;
    if (args == null)
        method = delegateClass.getMethod(methodName, new Class[] {});
        obj = method.invoke(delegate,new Object[] {});
    else
        method = delegateClass.getMethod(methodName, new Class[] {args.getClass()});
        obj = method.invoke(delegate, new Object[]{args});
   }This seems to have problems when I call the method from a class like:
execute("CategoryDelegate", "getCategoryById", new Integer(4144));(I get a NoSuchMethodException)
The method I am trying to execute in CategoryDelegate looks like:
public Category getCategoryById(int categoryId) throws DelegateExceptionI think it has to deal with the difference in the way we handle Primitive Wrappers and Objects. Wrapper we have to use Interger.TYPE and with the rest of the Objects we have to use obj.class.
Am I doing something wrong here? Any suggestions to make it work for primitive wrappers as well as Objects?