19 — Lambdas & Functional Programming

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▶️ java pkg1core/core21FunctionalProgramming.java

Lambda expressions (Java 8+)

1Calculator add = (a, b) -> a + b;2Runnable task = () -> System.out.println("run");3Consumer<String> print = s -> System.out.println(s);

A lambda implements a functional interface (exactly one abstract method).

Core functional interfaces

Method references

1Function<String, Integer> len = String::length;2Supplier<List<String>> factory = ArrayList::new;3list.forEach(System.out::println);

Shorthand when lambda just calls one method.

Custom functional interface

1@FunctionalInterface2interface Calculator {3    int op(int a, int b);4}

@FunctionalInterface is optional but catches mistakes.

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