List<? extends MyType>

java list generics bounded-wildcard
Lancelot picture Lancelot · May 27, 2009 · Viewed 59.4k times · Source

I have a Java question about generics. I declared a generic list: 

List<? extends MyType> listOfMyType;

Then in some method I try instantiate and add items to that list:

listOfMyType = new ArrayList<MyType>();
listOfMyType.add(myTypeInstance);

Where myTypeInstance is just an object of type MyType; it won't compile. It says:

The method add(capture#3-of ? extends MyType) in the type List<capture#3-of ? extends MyType> is not applicable for the arguments (MyType)

Any idea?

Answer

Surya picture Surya · May 27, 2009

You cannot do a "put" with extends . Look at Generics - Get and Put rule.

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