arrays.aslist adding derived class java

Question

So I have this:

class A{}
class B extends A {}
class C extends B {
    public String toString(){ return new String("C"); } 
    }
class D extends B {
    public String toString(){ return "D"; } 
    }

And then in main

List<A> list = Arrays.asList(new C(), new D());
        for (A a : list) {
            System.out.println(a.toString());
        }

I can compile this code and it prints: C D but on my friend's computer it won't compile. It has to deal with the Java version I am using ?

Well i don't know what error my friend got, he just told me that it doesn't compile. I was curious why my code worked on my computer while on my friend's computer didn't. Meanwhile I have found my answer. Thanks! — Ella Pînzaru, Feb 01 '15 at 21:19

score 5 · Accepted Answer · edited May 23 '17 at 12:06

5

That's right. You must be compiling on Java 8 while your friend is on Java 7.

In Java 7, the type of of the List returned by

Arrays.asList(new C(), new D());

would be inferred as List<B> and a List<B> cannot be assigned to a List<A>.

In Java 8, with some smarter generics, the compiler would infer a different type for the same expression, List<A>.

You can correct the Java 7 version with an explicit type argument

Arrays.<A>asList(new C(), new D());

edited May 23 '17 at 12:06

Community

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answered Feb 01 '15 at 20:11

Sotirios Delimanolis

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Thanks! My OOP professor told us in course that it doesn't compile and i was surprised to see that on my computer it compiled. – Ella Pînzaru Feb 01 '15 at 20:27

arrays.aslist adding derived class java

1 Answers1