When upgrading from Elasticsearch 8 to 9, do I need to update my application server Java code? I use the ES 8 Java API to talk to an ES 8 (and 9?) server. Is there any ES Java client version 9, for talking with ES server version 9? With some (breaking?) API changes? More on discuss.elastic.co

These are the topics that are covered with an indication if they are related to API design or not: [API] Do not Return Null to Indicate the Absence of a Value [API] Do not Use Arrays to Pass Values to and From the API [API] Consider Adding Static Interface Methods to Provide a Single Entry Point for Object Creation [API] Favor Composition With Functional Interfaces and Lambdas Over Inheritence [API] Ensure That You Add the @FunctionalInterface Annotation to Functional Interfaces [API] Avoid Overloading Methods With Functional Interfaces as Parameters [API arguably] Avoid Overusing Default Methods in Interfaces [not API] Ensure That the API Methods Check the Parameter Invariants Before They Are Acted Upon [not API] Do not Simply Call Optional.get() [not API] Consider Separating Your Stream Pipeline on Distinct Lines in Implementing API Classes So there are 6 or 7 items that directly are related to API design and 3 or 4 items that are just related to the implementation of API and not the API design as such. More on reddit.com