Do you somewhere have a class or interface named T, or are you using T as a concrete type name somewhere instead of as a type parameter (which means you might have forgotten somewhere else, for example in an enclosing class, to specify that T is a type parameter)? I can reproduce your problem with … Read more
I am meant to create a simple insertion sort method which sorts a series of generic names into alphabetical order. This should be simple, and I have already reviewed many other examples of insertion sort online, including on this site, yet I still cannot seem to obtain the correct output despite comparing my code, line-by-line, … Read more
This means that the type parameter must support comparison with other instances of its own type, via the Comparable interface. An example of such a class is provided in the Oracle tutorial Object Ordering. Note the similar pattern to T extends Comparable<T> in the excerpt below:
You can use an extension method.
When you do the second one, you’re making a new arraylist, you’re not trying to pretend the other list is an arraylist. I mean, what if the original list is implemented as a linkedlist, or some custom list? You won’t know. The second approach is preferred if you really need to make an arraylist from … Read more
The underlying issue is type erasure. The relevant implications of this means that an instance of the Stack class doesn’t know it’s type arguments at run-time. This is the reason why you can’t just use the most natural solution here, array = new T[maxSize]. You’ve tried to work around this by creating an array using … Read more
Perhaps you should consider using a HashSet. From the MSDN link:
Sometimes Java generics just doesn’t let you do what you want to, and you need to effectively tell the compiler that what you’re doing really will be legal at execution time. I usually find this a pain when I’m mocking a generic interface, but there are other examples too. It’s usually worth trying to work … Read more
When you do the second one, you’re making a new arraylist, you’re not trying to pretend the other list is an arraylist. I mean, what if the original list is implemented as a linkedlist, or some custom list? You won’t know. The second approach is preferred if you really need to make an arraylist from … Read more