# What is OpenJDK?

OpenJDK (Open Java Development Kit) is a free and open source implementation of the Java Platform, Standard Edition (Java SE). OpenJDK is the official reference implementation of Java SE since version 7.

> [wikipedia.org/wiki/OpenJDK](http://en.wikipedia.org/wiki/OpenJDK)

Java is a registered trademark of Oracle and/or its affiliates.

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# How to use this image

## Start a Java instance in your app

The most straightforward way to use this image is to use a Java container as both the build and runtime environment. In your `Dockerfile`, writing something along the lines of the following will compile and run your project:

```dockerfile
FROM %%REPO%%:7
COPY . /usr/src/myapp
WORKDIR /usr/src/myapp
RUN javac Main.java
CMD ["java", "Main"]
```

You can then run and build the Docker image:

```console
$ docker build -t my-java-app .
$ docker run -it --rm --name my-running-app my-java-app
```

## Compile your app inside the Docker container

There may be occasions where it is not appropriate to run your app inside a container. To compile, but not run your app inside the Docker instance, you can write something like:

```console
$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp %%REPO%%:7 javac Main.java
```

This will add your current directory as a volume to the container, set the working directory to the volume, and run the command `javac Main.java` which will tell Java to compile the code in `Main.java` and output the Java class file to `Main.class`.