From Applets to Backends — The Evolution of Java

A useful way to understand Java is as a series of eras. The language has changed shape several times — quietly enough that existing programs still work, but enough that the kinds of programs people write in Java have evolved dramatically.

Era 1: Applets in the browser (1995-2000)

The first thing the world saw Java do was animate stuff inside web pages. A Java applet was a small program (a .class file) that the browser downloaded and ran in a sandbox. Applets did simple animations, calculators, simple games, and proof-of-concept demos.

For a brief window in the late 1990s, applets looked like the future of interactive content on the web. They never quite lived up to that promise. They were slow to start, hard to secure, and quickly out-competed by JavaScript (which despite the confusing name is an unrelated language) and later by Flash.

Applets are now extinct. Modern browsers no longer support them. But they were Java's debut on the world stage and they are the reason millions of people first heard the word.

Era 2: Desktop and the early server (1996-2002)

Java grew up. Sun added Swing, a portable library for building desktop user interfaces. Companies started writing internal desktop tools in Java — administration consoles, monitoring dashboards, financial workstations.

At the same time, Java quietly invaded the server. The first version of servlets in 1997 let Java programs respond to web requests. JSP (JavaServer Pages) followed shortly. For the first time you could write a web application's backend in Java.

Era 3: The enterprise stack (2000-2010)

This is the era where Java became, for a generation, almost synonymous with "serious backend software." A bewildering ecosystem of standards grew up around the JVM: J2EE, EJB, JNDI, JMS, JTA, JSF, JAX-RS, and so on. Banks, insurers, airlines, and government departments built entire platforms on these foundations.

Some of these standards aged well; others were notoriously over-engineered. The reaction against the heavier parts produced a new style — lighter-weight frameworks like Spring (introduced in 2003), which is still the dominant backend framework in the Java world today.

You do not need to know the details of any of these frameworks to learn Java. They are downstream of the language. This course deliberately stays away from them so we can focus on the foundations that make all of them comprehensible later.

Era 4: Android and the mobile boom (2008-2017)

In 2008, Google launched Android. Every Android app was, for nearly a decade, written in Java. Suddenly there were hundreds of thousands of Java programmers who had nothing to do with enterprise backends or banking. They were writing mobile games, social apps, camera filters, fitness trackers.

Android did not use Sun's JVM directly. It used its own VM — first Dalvik, then ART — that ran a slightly different bytecode. But the source language was Java, and most of the Java standard library was available.

Today Kotlin has taken over for new Android code, but as we noted, Kotlin is itself a JVM language. The Java language is no longer the default on Android, but the Java platform still is.

Era 5: Big data and the JVM as a platform (2010-2020)

By 2010, "big data" was the headline. The dominant tools — Hadoop, Spark, Kafka, Elasticsearch, Cassandra — were written in Java or Scala, running on the JVM. Data engineering and data infrastructure became a major Java domain.

This era also saw the JVM platform mature: Scala (2004), Clojure (2007), and Kotlin (2011) all grew up enough to support production systems.

Era 6: Modern Java (2017-today)

Around Java 8 (2014), and especially Java 9 (2017), Oracle (which had acquired Sun in 2010) accelerated Java's evolution. New versions ship every six months now, instead of every two or three years. Recent versions have added:

• Lambdas and streams (Java 8, 2014) — a more functional style for working with collections.
• The module system (Java 9, 2017) — finer-grained packaging.
• Records (Java 16, 2021) — concise classes for plain data.
• Sealed classes (Java 17, 2021) — restrict who may inherit.
• Pattern matching for switch (Java 21, 2023) — richer conditionals.
• Virtual threads (Java 21, 2023) — massive concurrency without pain.

We will not use most of these advanced features in this course, but it is worth knowing they exist. Java is not standing still.

What got dropped

It is honest to mention things Java has given up on.

• Applets are gone. Browser plug-in security made them untenable.
• Web Start (a way of launching Java apps from a URL) is gone.
• Java EE (the enterprise standard) has been handed off to the Eclipse Foundation under the new name Jakarta EE.
• Sun itself is gone, acquired by Oracle in 2010.

What survived and grew is exactly the core of the original proposition: a portable, statically typed, garbage-collected OOP language running on the JVM.

QuestionSelect one

Which of the following best describes the trajectory of Java from 1995 to today?

It has been used mostly for graphical desktop applications

It started as a small portable language for embedded and browser use, and became a major language for servers, mobile, and data infrastructure

It has been replaced by Kotlin in almost all use cases

It has not changed since 1996

QuestionSelect one

Why are Java applets no longer used?

Because the JVM no longer supports them

Because browsers stopped supporting browser plug-ins, and JavaScript took over interactive content in web pages

Because Java itself has been deprecated

Because Sun never released them

The technical history is helpful, but Java's biggest legacy is not any one product. It is the way Java changed how programmers in general think about building software. That is the next page — and then we are done with the story and ready to write code.