What's the difference between `String.class` and `new Class[]{String.class}`?

Question

I'm brand new to Java. I have a question as follows:

class MyClass
{
    public MyClass(String s){}
}

MyClass MyObject;

Constructor ctor1 = MyObject.class.getConstructor(String.class); // #1
Constructor ctor2 = MyObject.class.getConstructor(new Class[]{String.class}); // #2

What's the difference between #1 and #2?

Answer 1

There is no difference.

The parameter type of getConstructor() is Class<?>..., which employs the varargs syntax, which is syntactic sugar that automatically converts a list of elements of any size (including zero) to an array.

To illustrate, these two calls are equivalent:

Constructor ctor1 = MyObject.class.getConstructor(String.class, Integer.class); // #1
Constructor ctor2 = MyObject.class.getConstructor(new Class[]{String.class, Integer.class}); // #2

---

Although I admire your enthusiasm of "looking under the hood" (using reflection), if you are new to java you may consider holding off until you have a firm grasp of the basics before learning how to circumvent them.

Answer 2

public Constructor<T> getConstructor(Class<?>... parameterTypes)
                              throws NoSuchMethodException,
                                     SecurityException

Have a look at defination of getConstructor(). It takes var-args parameter of type Class (Class<?> ...)

In your case, both the calls will eventually invoke the same constructor.