Eclipse警告——类是一个原始类型。应该参数化对泛型类型类的引用

import java.util.ArrayList;

public class ListOfClasses
{

    private ArrayList<Class> classes;

    public ArrayList<Class> getClasses() 
    {
        return classes;
    }

    public void setClasses(ArrayList<Class> classes) 
    {
        this.classes = classes;
    }
}
import java.util.ArrayList;

public class ListO