Usage of new Class<?>[]{} at getMethod

Question

Is there any difference between:

Method getIDMethod = MyInterface.class.getMethod("getId");

and

Method getIDMethod = MyInterface.class.getMethod("getId", new Class<?>[]{});

MyInterface is as follows:

public interface MyInterface {    
    AnotherInterface getId();    
}

Answer 1

No, there is no difference. An empty Class[] will be generated implicitly in the first case.

The Java Language Specification states

Invocations of a variable arity method may contain more actual argument expressions than formal parameters. All the actual argument expressions that do not correspond to the formal parameters preceding the variable arity parameter will be evaluated and the results stored into an array that will be passed to the method invocation (§15.12.4.2).

and about the invocation and evaluating arguments

If m is being invoked with k ≠ n actual argument expressions, or, if m is being invoked with k = n actual argument expressions and the type of the k'th argument expression is not assignment compatible with T[] , then the argument list (e1, ..., en-1, en, ..., ek) is evaluated as if it were written as (e1, ..., en-1, new |T[]| { en, ..., ek }) , where |T[]| denotes the erasure (§4.6) of T[] .

Technically, it would be equivalent to

new Class[]{} // instead of new Class<?>[]{}

Answer 2

No, there is no difference between these two, empty array means method has no parameter

but if your method accept any parameter you must use second form like

Method getIDMethod = MyInterface.class.getMethod("setId", new Class<?>[]{String.class});
public interface MyInterface {    
    public void setId(String arg);    
}

here is declaration of getMethod method in Class , as you see second parameter is params array and there is no difference between sending empty array or doesn't send anything

public Method getMethod(String name, Class<?>... parameterTypes)
    throws NoSuchMethodException, SecurityException {
// be very careful not to change the stack depth of this
// checkMemberAccess call for security reasons 
// see java.lang.SecurityManager.checkMemberAccess
    checkMemberAccess(Member.PUBLIC, ClassLoader.getCallerClassLoader());
    Method method = getMethod0(name, parameterTypes);
    if (method == null) {
        throw new NoSuchMethodException(getName() + "." + name + argumentTypesToString(parameterTypes));
    }
    return method;
}