RFR: 8197594 - String and character repeat

[Remi Forax]

I'm not sure we need 4, it's just a convenient method that may be slower than if the user code calls toString() (because of profile pollution),
so i'm not sure i pull it's own weight.

And about adding a default method into CharSequence, the default method should return a CharSequence or String ? and what about the other implementations, AbstractStringBuilder and CharBuffer at least ? 

Rémi

----- Mail original -----
> De: "Jim Laskey" <james.laskey at oracle.com>
> À: "Brian Goetz" <brian.goetz at oracle.com>
> Cc: "core-libs-dev" <core-libs-dev at openjdk.java.net>
> Envoyé: Jeudi 15 Février 2018 18:34:19
> Objet: Re: RFR: 8197594 - String and character repeat

> Very reasonable approach.
> 
> 
>> On Feb 15, 2018, at 1:31 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
>> 
>> I suggest merging 1 and 4 by making it an instance method on CS with a default
>> in CS and an override on string and string builder?
>> 
>> Sent from my MacBook Wheel
>> 
>>> On Feb 15, 2018, at 9:20 AM, Jim Laskey <james.laskey at oracle.com> wrote:
>>> 
>>> This is a pre-CSR code review [1] for String repeat methods (Enhancement).
>>> 
>>> The proposal is to introduce four new methods;
>>> 
>>> 1. public String repeat(final int count)
>>> 2. public static String repeat(final char ch, final int count)
>>> 3. public static String repeat(final int codepoint, final int count)
>>> 4. public static String repeat(final CharSequence seq, final int count)
>>> 
>>> For the sake of transparency, only 1 is necessary, 2-4 are convenience methods.
>>> In the case of 2, “*”.repeat(10) performs as well as String.repeat(‘*’, 10).
>>> 3 and 4 convert to String before calling 1.
>>> 
>>> Performance runs with jmh (results as comment in [2]) show that these
>>> methods are significantly faster that StringBuilder equivalents.
>>> - fewer memory allocations
>>> - fewer char to byte array conversions
>>> - faster pyramid replication vs O(N) copying
>>> 
>>> I left StringBuilder out of scope. It falls under the category of
>>> Appendables#append with repeat. A much bigger project.
>>> 
>>> All comments welcome. Especially around the need for convenience
>>> methods, the JavaDoc content and expanding the tests.
>>> 
>>> — Jim
>>> 
>>> [1] webrev: http://cr.openjdk.java.net//oj/home/jlaskey/8197594/webrev-00
>>> [2] jbs: https://bugs.openjdk.java.net/browse/JDK-8197594
>>>