Why do I get Java.lang.IllegalArgumentException: wrong number of arguments while invoking a method with varargs using Reflection [duplicate]

Question

I have a method in a class as below

  class Sample{

    public void doSomething(String ... values) {

      //do something
    }

    public void doSomething(Integer value) {

    }

  }


//other methods
.
.
.

Now I get IllegalArgumentException: wrong number of arguments below

Sample object = new Sample();
Method m = object.getClass().getMethod( "doSomething", String[].class );
String[] arr = {"v1","v2"};
m.invoke( object, arr ) // exception here

Answer 1

Wrap your String array in an Object array:

Sample object = new Sample();
Method m = object.getClass().getMethod("doSomething", String[].class);
String[] arr = {"v1", "v2"};
m.invoke(object, new Object[] {arr});

A varargs argument, even though it may be comprised of multiple values, is still considered to be one single argument. Since Method.invoke() expects an array of arguments, you need to wrap your single varargs argument into an arguments array.