Here are apps written in Java:

Minecraft: Minecraft, a hugely popular sandbox game developed by Mojang Studios, is written in Java. It uses Java's cross-platform capabilities to ensure compatibility across different operating systems. The game's world-building mechanics and various features are implemented using Java code.

IntelliJ IDEA: IntelliJ IDEA is a powerful and widely used integrated development environment (IDE) for Java development. Ironically, this app itself is written in Java. It offers extensive features and tools to streamline the software development process and enhance productivity for Java developers.

Apache Tomcat: Apache Tomcat is a popular web server and servlet container that is written in Java. It provides an environment to run Java-based web applications. Tomcat is widely used for deploying and running Java web applications, and it serves as the foundation for many Java-based web frameworks and applications.

jMonkeyEngine: jMonkeyEngine is a modern and feature-rich game engine for Java-based game development. It provides a set of libraries and tools that simplify the creation of 3D games. The engine itself is written in Java and offers developers the flexibility and power to build immersive gaming experiences.