java-guide

A guide to modern Java (Java 17)

This guide is about learning Java from scratch if you know a bit of C or JavaScript.

This is a Work in progress, it should be ready when the next LTS of Java (Java 17) will be released. All the codes run with Java 14 with the preview features enabled.

Note: if you are looking to only what's new in Java 14 I have set of slides for that.

Content

0. genesis.md
1. basic_types.md
2. methods.md
3. jshell_vs_java.md
4. numbers.md
5. control_flow.md
6. interface.md
7. lambda.md
8. list_and_map.md
9. string_formatting.md
10. class_and_encapsulation.md
11. equals_hashCode_toString.md
12. contract.md
13. modifiable_vs_mutable.md
14. null_and_optional.md
15. inheritance.md
16. exception.md
17. enum.md
18. nested_classes.md
19. array.md
20. implementing_interface.md
21. generics.md
22. wrapper.md
23. variance.md
24. limitation_of_generics.md
25. stream.md
26. collector.md
27. data_structure.md
28. sort.md

Using Java Shell (jshell)

Each chapter comes with executable examples that you can run using jshell.

To get the examples, just clone this repository

git clone http://github.com/forax/java-guide

Then run jshell (at least Java 14 version)

jshell --enable-preview

Then you can copy paste the examples inside jshell and see by yourself.

To quit use '/exit', to enable verbose error messages '/set feedback verbose', otherwise to get the help type '/help'

Using Jupyter notebook

on the cloud

You can run it directly in your browser

or using docker

You need to have docker already installed, then

• get the docker image from dockerhub

  docker pull forax/java-guide

• run the docker image in a container

  docker run -p 8888:8888 forax/java-guide

• open your browser using the tokenId printed on the console

  firefox http://localhost:8888/?token=tokenId

or install everything on your laptop

You need to have python3 and Java 14 already installed, then

• clone this repository

  git clone http://github.com/forax/java-guide
  cd java-guide

• install jupyter

  pip install notebook

• install the ijava 1.3.0 kernel (from Spencer Park)

  wget https://github.com/SpencerPark/IJava/releases/download/v1.3.0/ijava-1.3.0.zip
  python3 install.py --sys-prefix

• patch it with the repository file kernel.json
  list all kernels to see if the java kernel is installed

  jupyter kernelspec list

  then copy the file kernel.json from the folder docker to the java kernel directory

  cp docker/kernel.json /path/to/jupyter/kernels/java

• set the env compiler option enabling the preview features

  export IJAVA_COMPILER_OPTS="--enable-preview -source 14"

• run the notebook

  cd jupyter
  jupyter notebook

Build markdown and jupyter files from jshell files

The markdown files (.md) and the jupyter files (.ipynb) are derived/generated from the jshell files using a small Java script.

Using java 14

java --source 14 --enable-preview build/build.java