hints.md 1.8KB
This exercise introduces generics.
To make the tests pass you need to construct your class such that it accepts any type of input, e.g. Integer or String.
Generics are useful because they allow you to write more general and reusable code.
The Java List and Map implementations are both examples of classes that use generics.
By using them you can construct a List containing Integers or a list containing Strings or any other type.
There are a few constraints on the types used in generics.
One of them is that once you've constructed a List containing Integers, you can't put Strings into it.
You have to specify which type you want to put into the class when you construct it, and that instance can then only be used with that type.
For example you could construct a list of Integers:
List<Integer> someList = new LinkedList<>();
Now someList can only contain Integers. You could also do:
List<String> someOtherList = new LinkedList<>()
Now someOtherList can only contain Strings.
Another constraint is that any type used with generics cannot be a primitive type, such as int or long.
However, every primitive type has a corresponding reference type, so instead of int you can use Integer and instead of long you can use Long.
It can help to look at an example use case of generics to get you started.