Confused about `toArray(T[] a)` method in java

Question

The List has a method toArray such as:

<T> T[] java.util.ArrayList.toArray(T[] a)

When calling this method, I should create a new instance and pass it toArray(new MyElementClass[0]).

Could it be defined like this:

<T> T[] java.util.ArrayList.toArray(Class<T>)

By calling toArray(MyElementClass[].class), can it be more effective?

Probably yes, although you could always keep a number of constants with zero-length arrays of each of the types that you need. But the question is very hypothetical, since you can't change the API classes. — Erwin Bolwidt
– Erwin Bolwidt, Commented Jan 11, 2015 at 6:37
List is interface and it does not have method called "toArray". There is implementation of this interface called ArrayList which does. Just to not confuse other people — rkosegi
– rkosegi, Commented Jan 11, 2015 at 7:04
If it was <T> T[] toArray(Class<T>), then you would have to call it as toArray(MyElementClass.class) — newacct
– newacct, Commented Jan 12, 2015 at 0:53

Community · Accepted Answer · 2017-05-23 10:33:19Z

3

It would be. However, the original method is given for backwards compatibility.

See this

edited May 23, 2017 at 10:33

CommunityBot

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answered Jan 11, 2015 at 6:38

k_g

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newacct · Accepted Answer · 2015-01-12 06:46:35Z

1

The way toArray is now, it allows you to re-use an array (it will use the given array if it is of sufficient size) rather than always needing to allocate a new one.

answered Jan 12, 2015 at 6:46

newacct

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