Instantiating an inner class

Question

I have a utility method and when irrelevant logic is removed from it, the simplified method would look like this:

public static  List<         


        

Answer 1

If it's genuinely an inner class instead of a nested (static) class, there's an implicit constructor parameter, which is the reference to the instance of the outer class. You can't use Class.newInstance at that stage - you have to get the appropriate constructor. Here's an example:

import java.lang.reflect.*;

class Test
{
    public static void main(String[] args) throws Exception
    {
        Class clazz = Outer.Inner.class;

        Constructor ctor = clazz.getConstructor(Outer.class);

        Outer outer = new Outer();
        Outer.Inner instance = ctor.newInstance(outer);
    }
}

class Outer
{
    class Inner
    {
        // getConstructor only returns a public constructor. If you need
        // non-public ones, use getDeclaredConstructors
        public Inner() {}
    }
}