Cannot create a generic array of ... in Java

Question

I'm getting an error that I can't understand. I defined the class Couple in Java this way :

public class Couple<T1, T2>{
private T1 t1;
private T2 t2;
 public Couple(T1 t1, T2 t2) {
 this.t1 = t1;
 this.t2 = t2;
 }
 public Couple() {
 this.t1 = null;
 this.t2 = null;
 }
 public T1 getFirst(){return t1;}
 public T2 getSecond(){return t2;}
}

And in an another class, I try to define an array this way :

Couple<byte[], byte[]>[] res = new Couple<byte[], byte[]>[10];

But Eclipse tells me the error "Cannot create a generic array of Couple<byte[], byte[]> ". Well, the thing that I don't understand is that I mentionned that I wanted a couple of byte[], so there is no genericity at this point, am I wrong ?

• JB Nizet: You may not create arrays of generic types. Couple<byte[], byte[]> is a generic type, and you're trying to create an array of this type. So that won't compile. Use a List<Couple<<byte[], byte[]>> instead.
• Raoul722: Ok, I will try it. Thought that if I mentionned the type of couple there was no more genericity. Ty anyway
• Mike Nakis: As DennisW said, you cannot do that, Java is quite peculiar about it. But you can do this: Couple<byte[], byte[]>[] res = new Couple[10]; You will probably get some warnings, suppress them. Oh, and, by the way: this has absolutely nothing to do with eclipse.
• Svetlin Zarev: possible duplicate of How to create a generic array in Java?

Answer 1

Java generics are not reified, which means that the 'implementations' are not classes in their own right. The fact that you can't create arrays of generic types is an inherent limitation of the language.

I'd recommend you to use a List instead of an array.