mtumilowicz/java11-lambda-type-inference

Exploring basic features of lambda type inference in Java 11.

java11-lambda-type-inference

The main goal of this project is to show how to use type inference for lambda expressions.

Reference: https://medium.com/the-java-report/java-11-sneak-peek-local-variable-type-inference-var-extended-to-lambda-expression-parameters-e31e3338f1fe
Reference: https://stackoverflow.com/questions/50225672/java-11-local-variable-syntax-for-lambda-parameters-applications

preface

We have three ways to provide types to lambdas:

• explicit

  Predicate<String> isLowercase = (String str) -> str.equals(str.toLowerCase());
  

• implicit

  Predicate<String> isLowercase = str -> str.equals(str.toLowerCase());
  

• inference

  Predicate<String> isLowercase = (var str) -> str.equals(str.toLowerCase());
  

As you may see - java has two mechanisms for type inference on local lambda expression variables (as mentioned above - implicit and inference).

Previously (prior to 11), if we wanted to use modifiers on lambda formals we had to use explicit syntax, now it is possible to write:

Predicate<String> isLowercase = (@NonNull var str) -> str.equals(str.toLowerCase());

which is a very concise, coherent and elegant way.

project description

In LambdaLocalTypeInferenceTest we provide full examples of the mentioned functionality.