Added lesson2

.gitmodules

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+[submodule "Core_JAVA_Volume1"]
+	path = Core_JAVA_Volume1
+	url = git@github.com:specter01wj/Core_JAVA_Volume1.git

Core_JAVA_Volume1

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+Subproject commit 8ca9c76bf17e49e0d4654973fff7889caf4644e8

Dockerfile

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+FROM openjdk:slim-buster
+COPY Core_JAVA_Volume1/corejava/v1ch02/ImageViewer /usr/src/myapp
+WORKDIR /usr/src/myapp
+RUN javac ImageViewer.java
+CMD ["java", "ImageViewer"]

lesson2.md

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+# Lesson 2: The Java Programming Environment
+
+## Run as server
+
+For headless application (run as server), we can use docker.
+
+After create `FILE.java`, create a `Dockerfile`
+
+```
+FROM openjdk:slim-buster
+COPY <script location> /usr/src/myapp
+WORKDIR /usr/src/myapp
+RUN javac <script>.java
+CMD ["java", "<script name>"]
+```
+
+Then run and build the Docker image
+
+```
+$ docker build -t my-java-app .
+$ docker run -it --rm --name my-running-app my-java-app
+```
+
+## If run as desktop application
+
+First, compile Java
+
+```
+$ javac <script>.java
+```
+
+Then, run Java
+
+```
+$ java <script>
+```
+
+## Run jshell for interaction
+
+Methods:
+
+* 1: `$ jshell`
+* 2: using docker: `docker run --rm -it -v "$(pwd)":/usr/src openjdk:slim-buster`