SOLR-16318: WIP - Use up to JDK 11 features

[risdenk]

https://issues.apache.org/jira/browse/SOLR-16318

Description

• Use enhanced for loops
• Avoid type declaration when <> can be used
• Use computeIfAbsent
• use Objects.requireNonNullElse to simplify if/else statements
• Simplify lambda statements
• Collections.sort -> list.sort
• Use string .contains instead of checking indexOf
• Avoid unnecessary boxing/unboxing

[risdenk]

Thanks @madrob for the quick review. I threw it up to review myself and wasn't expecting comments yet :) I agree with your findings and many probably repeat throughout. I'll clean it up over the next few days.

[epugh]

I am not really up on the new stuff in JDK 11 @risdenk so probably not the best person to review... ;-)

[risdenk]

@epugh mostly an FYI since you were going through intelli warnings - these are also intellij warnings/findings behind the scenes.

[risdenk]

This is being broken into pieces slowly.