Java Development: JDK Installation and Environment Configuration

Preface

Environment configuration is the most basic part of development, but recently many newcomers have been asking how to install the JDK and configure the environment, so I decided to write a post about it. Note that development on Windows and Linux platforms is different. Developing Java on Windows requires you to manually configure JDK environment variables, while most Linux systems do not need this—installing OpenJDK is enough (many distributions may even come with OpenJDK preinstalled), which is quite convenient.

Downloading the Java JDK

Windows Platform

Open Oracle's JDK website: http://www.oracle.com/technetwork/java/javase/downloads/index.html The website looks like this. Make sure you check the version when downloading.

The version chosen in this article is JDK 8

Click the download button to download. After the download is complete, open it and install. Key point: Remember to note down the installation directory!! You'll need it later

Linux Platform

On Linux, you can choose OpenJDK or the JDK provided by Oracle. There are differences between the two. Here's a recap of the differences between OpenJDK and JDK. (The following is quoted from Zhihu user Aloys寒风)

Historically, OpenJDK is the open-source version of the JDK, released under the GPL (General Public License) (the "open" mentioned by the OP refers to open source). By the time of JDK 7, OpenJDK had already become the main trunk of JDK 7 development. SUN JDK 7 was released based on OpenJDK 7; most of the source code is the same, with only a small portion replaced. It was released under the JRL (Java Research License). As for OpenJDK 6, it has an even more complicated side: first, OpenJDK 6 is a branch of JDK 7, and it tries as much as possible to remove the new features of Java SE 7 so that it conforms as much as possible to the Java 6 standard. The differences between JDK and OpenJDK can be summarized as follows:

Different licenses: OpenJDK is released under the GPL V2 license, while SUN JDK is released under the JRL. Although both licenses are open source, they differ in usage in that GPL V2 allows commercial use, while JRL only allows personal research use. OpenJDK does not include Deployment functionality: deployment features include: Browser Plugin, Java Web Start, and the Java Control Panel, which cannot be found in OpenJDK.

OpenJDK source code is incomplete: This is easy to understand. In OpenJDK, which uses the GPL license, some of SUN JDK's source code cannot be opened to OpenJDK due to proprietary rights issues. The most significant part is the code for the optional SNMP component in JMX. Therefore this source code that cannot be opened is made into a plug for use when compiling OpenJDK; you can also choose not to use the plug. Icedtea developed source code with the same functionality for these incomplete parts (OpenJDK 6), making OpenJDK more complete.

Some source code is replaced with open-source code: Due to proprietary rights issues, a lot of source code whose rights do not belong to SUN was replaced with open-source code that has the same functionality, for example the font rasterization engine, replaced with Free Type.

OpenIDK only includes the most minimal JDK: OpenJDK does not include other software packages, such as Rhino Java DB JAXP..., and packages that can be separated are also separated as much as possible, but most of these are free software, and you can download and add them yourself. Cannot use the Java trademark: This is easy to understand. On a machine with OpenJDK installed, entering java -version displays OpenJDK, but if it is OpenJDK using the Icedtea patch, it displays java.

In short, in the Java ecosystem, there are still many non-free components, and the development of the source code is not thorough enough.

So, on Linux, should you use JDK or OpenJDK?? I think OpenJDK is completely sufficient, and it's also convenient to install. Enter jdk in the package manager to install, and what you get is OpenJDK.

Debian-based install: sudo apt install jdk

Red Hat-based install: yum apt install jdk

SUSE install: sudo zypper in jdk

If you insist on using Oracle's JDK, then go to the Oracle official website to download it. The download URL is above. As for the installation method, it varies slightly across Linux distributions. Anyone who can tinker with Linux shouldn't have a problem installing a piece of software.

Path Configuration

Alright. I admit the most annoying thing about Java is having to configure environment variables, especially on Windows. Can't you just have it configured automatically after installation?! Python can be that convenient, but you can't = =

Windows Platform Configuration

First, open the path you noted down after the installation above.

Then press Win+R to open Run. Enter: control to open the Control Panel

I'm using an English version of the system, but you can follow along with the screenshots the same way. Select "System".

Select "Advanced system settings"

Environment Variables

This opens the environment variable editor

First, create a JAVA_HOME environment variable. The value is the JDK installation location from earlier.

Next, add a CLASSPATH variable. Value: .;%JAVA_HOME%\lib;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar;

Finally, add javahome and classpath to the system's Path. Click "Add". Add the following two paths. %JAVA_HOME%\bin %JAVA_HOME%\jre\bin If you're not on Windows 10 and don't have this Path editor, append the following to the original Path variable: ;%JAVA_HOME%\bin;%JAVA_HOME%\jre\bin Note there is a semicolon at the front Then click "OK".

Garbled Text When Running Java on Windows

It works fine on Linux and macOS; the problem only appears in the Windows environment, and running through an IDE is also fine

It's fair to call Windows garbage at this point, right?

Solution:

Add a new user variable

JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF-8

After that, when you run Java commands in Windows terminal, there's no more garbled text~

Testing

Open the console and enter jave -version Configuration completed successfully!