Thread: please tell me how to creat an array of an inner cclass;

For an array, no.
The correct syntax would be:

outer.inner[] i = new outer.inner[5];

However, if you only wanted a single instance of the inner class, something similar to your syntax would work:

outer o = new outer();
outer.inner i = o.new inner();

If you're unsure if something is correct, you can always try it out.

Something I would recommend is to simply declare the inner class static

public class Outer
{
    static class Inner
    {}
}

To create a new array it would use the same syntax, but to create a new instance of Inner, you just need to do this:

Outer.Inner i = new Outer.Inner();