Java is an object-oriented programming language known for its robustness, security, and platform independence. It is widely used for developing enterprise web applications, distributed systems, and desktop software. The language's design avoids complexities like explicit pointers and multiple inheritance found in C++.

Official Java images are hosted on Docker Hub at java. The community's adoption of Docker for Java, while growing, has seen less comprehensive official documentation compared to some other languages.

Comparing the size of base images across different ecosystems reveals that the official Java image is relative large, often exceeding 600 MB. In contrast, images for languages like .NET Core or Python can be significantly smaller, with .NET Core runtime images around 200 MB.

Using Docker for Java development addresses several practical concerns:

• Eliminates the need to install and configure a Java Development Kit (JDK) local.
• Allows for easy switching between Java versions by simply changing the base image.
• Provides a consistent, isolated environment that can be shared across teams.

As a demonstration, we can create a simple "Hello World" application.

// HelloWorld.java
import java.time.LocalDateTime;

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Greetings from inside the container!");
        System.out.println("Current time: " + LocalDateTime.now());
    }
}

A Dockerfile is required to containerize this application. The following example uses a Java 11 base image.

# Dockerfile
FROM openjdk:11-jdk-slim

WORKDIR /usr/src/app

COPY HelloWorld.java .

RUN javac HelloWorld.java

CMD ["java", "HelloWorld"]

To build the Docker image, run the following command in the directory containing the Dockerfile and source file:

docker build -t java-demo-app .

Once the build completes successfully, execute the containerized application:

docker run --rm java-demo-app