why we cannot use double as a generic T?

Question

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Why don't Generics support primitive types?

Why we cannot use double as a T, instead we have to use Double?

we will have compile error if using List

score 1 · Accepted Answer · answered Oct 14 '11 at 03:22

1

Generics type parameter must be a sub-class of java.lang.Object.

answered Oct 14 '11 at 03:22

KV Prajapati

score 1 · Answer 2 · answered Oct 14 '11 at 03:22

1

double is not an Object,You can use Double

answered Oct 14 '11 at 03:22

刘伟科

+1. Also, see http://download.oracle.com/javase/tutorial/java/generics/gentypes.html (it specifically mentions you cannot use primitives). – Snowy Coder Girl Oct 14 '11 at 03:25
@Rachel I think the OP understands that generic types cannot be primitives. The question is: _why not?_ – Matt Ball Oct 14 '11 at 03:26
1

How is this an answer? It doesn't explain the why at all, and the OP already knew he had to use `Double` instead. – Mark Peters Oct 14 '11 at 03:27
I think the OP wants to konw 'how' but not 'WHY'. – 刘伟科 Oct 14 '11 at 03:58

score 0 · Answer 3 · answered Oct 14 '11 at 03:24

0

double is primitive data type of Java, while Generics type needs an java.lang.Object, and Double is an Object

answered Oct 14 '11 at 03:24

Quincy

score 0 · Answer 4 · answered Oct 14 '11 at 03:27

0

T must be non-primitive data type. It may seem inconvenient at first glance, but there is auto-boxing, that is you can have something like this:

List<Double> list = new ArrayList<Double>();
double x = 5.0d;
list.add(x);
double y = list.get(0);

answered Oct 14 '11 at 03:27

Tair

As with @LiuwkCn's answer: this does not answer the question at all. It states the "what" (which the OP appears to have already figured out), not the "why." -1 – Matt Ball Oct 14 '11 at 03:29

4 Answers4