I am using a very primitive Java that doesn't have Generics, and also I can't use reflection.

I want to create a generic list so it would be typed safe (i.e. I only have a list that contains Objects and I want to create a list that contains specific object and not a mix).

On the other hand I also don't want to create a different class for each possible list.

Is there any other way to do that without the use of Generics?


Yes, there is. It will be fully run-time solution (no compile-time type checking), but it's worth it (you will get an early crash on first attempt to insert an object with wrong type).

public class TypedArrayList extends ArrayList {
    private final Class elementType;

    public TypedList(Class elementType) {
        this.elementType = elementType;

    public boolean add(Object element) {
        // preffered version, use it if it's available on your platform
        // if (!elementType.isInstance(element)) {
        if (!elementType.equals(element.getClass())) {
             throw new IllegalArgumentException("Object of type " + element.getClass() + "passed to List of "+ elementType);
        return super.add(element);

    // override other methods
    // that need type checking


TypedArrayList list = new TypedArrayList(String.class);
list.add(new Object()); // throws exception

You can do the same for LinkedList and any other list type.

  • 2
    Instead of equals, you might want to use isInstance so it'll also accept child types. – Idan Arye Apr 6 '14 at 12:50
  • @IdanArye Do you mean instanceof? – Azar Apr 6 '14 at 13:31
  • Class.isInstance(Object) (its in the comment in posted code fragment) – Maciej Chałapuk Apr 6 '14 at 13:35
  • @Azar Not exactly. instanceof is a keyword and in order to use it you to write the name of the class inside the code. isInstance is a method of Class that you can use when you have the class as class object, and does the same thing as instanceof. – Idan Arye Apr 6 '14 at 13:36
  • @MaciejChałapuk Sorry, didn't notice it. Still - isInstance as been around since Java 1.1 so I doubt it's not available on any Java platform that's still being used. Asker's platform is old, but it can't be that old... – Idan Arye Apr 6 '14 at 13:38

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