Modern Java Features

Java has evolved rapidly since adopting a six-month release cadence in 2017. This lesson covers the most impactful features from Java 8 through Java 21, including lambdas, streams, records, sealed classes, pattern matching, and virtual threads.

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Lambda Expressions (Java 8)

A lambda is a concise way to represent a function (an implementation of a functional interface):

// Before lambdas
Comparator<String> cmp = new Comparator<String>() {
    @Override
    public int compare(String a, String b) {
        return a.length() - b.length();
    }
};

// With a lambda
Comparator<String> cmp = (a, b) -> a.length() - b.length();

Lambda Syntax

// No parameters
Runnable r = () -> System.out.println("Running");

// One parameter (parentheses optional)
Consumer<String> greet = name -> System.out.println("Hello, " + name);

// Multiple parameters
BiFunction<Integer, Integer, Integer> add = (a, b) -> a + b;

// Multi-line body
Comparator<String> cmp = (a, b) -> {
    int diff = a.length() - b.length();
    return diff != 0 ? diff : a.compareTo(b);
};

Common Functional Interfaces