Question

Hi I am trying to create a generic method that takes in a parameter which type is an abstract parameterised class. Inside the method I want to create a instances of the passed parameter given it is a subclass of the abstract type since we cannot instantiate abstract classes.

However I am having some issues. And the error message says the RuleType cannot be resolved to a type which is not surprising anyway but I don’t know how can I accomplish this.
My current code is below.

private <F extends AbstractRule<T>, T> void applyRyle(F cRule,ArrayList<T> aFeatures)
{

    Class RuleType = cRule.getClass();


    // if the parameter passed is a subclass of AbstractRule create some objects
    if(!RuleType.getSuperclass().getName().equals("AbstractRule"))
    {
        ArrayList<RuleType<T>> aRules = new ArrayList<RuleType<T>>();
        for(int i = 0; i < 10; i++)
        {

            RuleType<T> aRule= new RuleType<T(pattern.getMatrices().size(), 2,aFeatures);
            aRule.initialise(aRule.getMaxLocalLevel());
            aRules.add(aRule);
        }
    }

Answer 1

Some of this can be done by using reflection:

private <F extends AbstractRule<T>, T> void applyRyle(F cRule, ArrayList<T> aFeatures)
{
     Class<? extends F> ruleType = cRule.getClass();
     // if the parameter passed is a subclass of AbstractRule create some objects
     if(! ruleType.getSuperclass().getName().equals("AbstractRule"))
     {
         ArrayList<? extends F> aRules = new ArrayList<? extends F>();
         for(int i = 0; i < 10; i++)
         {
             F aRule =
                 ruleType
                     .getConstructor(int.class, int.class, ArrayList.class)
                     .newInstance(pattern.getMatrices().size(), 2, aFeatures);
             aRule.initialise(aRule.getMaxLocalLevel());
             aRules.add(aRule);
         }
     }

though it’s probably not the best way to accomplish what you really want.