Test and trust Class.isInstance or try and catch Class.cast ?

Question

I found this related thread, with no answer to my question.
In the below code, there is a certain level of redundancy in that I am checking that I can do the Class.cast() prior to doing it, via Class.isInstance().
I can either omit the isInstance() check and just count on cast() throwing an exception, or I can ignore the ClassCastException (do nothing in the catch block, as shown below).
Which is better? Is it faster if I just omit the instance check and let cast() detect the errors? Is there a style convention here?
    protected <T extends ParentClass> List<T> getItemsOfType(Class<T> clazz){
        List<T> retval = new ArrayList<T>();
        for(ParentClass t : items.values()){
            if(clazz.isInstance(t)){
                try{
                    retval.add(clazz.cast(t));
                catch(ClassCastException cce){
                    // should never happen
    }Thanks for your time

Answer 1

Derrick.Rice wrote:
I found this related thread, with no answer to my question.
In the below code, there is a certain level of redundancy in that I am checking that I can do the Class.cast() prior to doing it, via Class.isInstance().
I can either omit the isInstance() check and just count on cast() throwing an exception, or I can ignore the ClassCastException (do nothing in the catch block, as shown below).
Which is better? Is it faster if I just omit the instance check and let cast() detect the errors? Is there a style convention here?Whatever you decide, just keep in mind that there is a semantic difference too:
if(clazz.isInstance(t)) retval.add(clazz.cast(t));will only add instances of the requested class, whereas
try { retval.add(clazz.cast(t)); } catch(ClassCastException e) {} will also add null values.