RiakIndex type signature is incorrect [JIRA: CLIENTS-690]

[TJC]

While trying to work out how to access indexes via Scala, I had a lot of trouble getting the result of StringBinIndex.named("example") to work with the parameterised riakObject.getIndex method.

After discussion on a Scala list, several Java devs said that the problem stems from the RiakIndex type signature being incorrect.

Instead of:
  public  <V extends RiakIndex, T extends RiakIndex.Name<V>> V getIndex(T name) 
It should be:
  public  <V extends RiakIndex<?>, T extends RiakIndex.Name<V>> V getIndex(T name) 

I myself am not a strong Java dev and so am not able to verify this, but I thought I should forward it along.

[Basho-JIRA]

Fix is included on the https://github.com/basho/riak-java-client/tree/scala-improvements branch

_[posted via JIRA by Alexander Moore]_

[alexmoore]

I fixed this type signature, as the <?> is more correct, but Scala still has trouble inferring the types. Left a comment in the javadocs to address this.

Unsure of what work will need to be done to get Scala to infer the types correctly (probably a rewrite of RiakIndex et al.).