1. Introduction

Java 8, released in March 2014, marked one of the most transformative updates in Java’s history. It introduced powerful new features that brought functional programming constructs to the language and enhanced productivity. It is defined by the official platform specification: JSR 337 – Java SE 8 Platform Specification. In this article, we’ll explore five essential features introduced in JDK 8.

2. Lambda Expressions (JEP 126)

JEP 126 introduced lambda expressions, allowing concise representation of functional interfaces.

List<String> names = Arrays.asList("Alice", "Bob", "Charlie");
names.forEach(name -> System.out.println("Hello, " + name));

Why it matters: Enables functional-style programming and reduces boilerplate code.

3. Streams API (JEP 107)

JEP 107 added the Streams API for processing collections in a declarative and parallelizable way.

List<String> words = Arrays.asList("Java", "Stream", "API", "Example");
long count = words.stream()
    .filter(w -> w.length() > 4)
    .count();
System.out.println("Words longer than 4 letters: " + count);

Why it matters: Makes complex data transformations readable and efficient.

4. Default Methods in Interfaces (JEP 126)

Also part of JEP 126, default methods allow interfaces to provide method implementations.

interface Greetable {
    default void greet() {
        System.out.println("Hello!");
    }
}

class User implements Greetable {}

Why it matters: Enables interface evolution without breaking existing implementations.

5. java.time API (JSR 310)

The new java.time package, specified in JSR 310, modernizes date and time handling.

LocalDate today = LocalDate.now();
LocalDate birthday = LocalDate.of(1990, Month.JULY, 15);
Period age = Period.between(birthday, today);
System.out.println("You are " + age.getYears() + " years old.");

Why it matters: Fixes flaws in java.util.Date and Calendar with an immutable and fluent API.

6. New Methods on Collections and Utilities

Java 8 enhanced existing libraries with utility methods like Map.forEach(), List.sort(), and Comparator.comparing().
These changes were introduced as standard API improvements without specific JEPs.

Map<String, Integer> map = new HashMap<>();
map.put("A", 1);
map.put("B", 2);
map.forEach((k, v) -> System.out.println(k + ": " + v));

Why it matters: Reduces verbosity and makes code more expressive.

7. Conclusion

Java 8 laid the foundation for modern Java development with a blend of functional programming and enhanced APIs. These features remain widely used and continue to shape how developers write Java today. Understanding them is essential for writing clean, modern, and efficient Java code.

You can find the complete code of this article here in GitHub.