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Java Development Kit (JDK) is the SDK for Java. This document takes JDK 1.7 and 1.8 as examples to describe how to install and configure JDK under Windows and Linux systems.

Windows

1. Downloading a JDK

Go to the Oracle website to download the desired JDK version.

2. Installation

Install the JDK as instructed. You can specify the installation paths (C drive by default), for example, as D:\Program Files\Java\jdk1.8.0_31 and D:\Program Files\Java\jre1.8.0_31.

3. Configuration

After the installation is completed, right-click Computer, and then click Properties > Advanced system settings > Environment Variables > System variables > New to configure the software.
Variable name (N): JAVA_HOME
Variable value (V): D:\Program Files\Java\jdk1.8.0_31 (Configure according to your actual installation path).

Variable name (N): CLASSPATH
Variable value (V): .;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar; (Note that the variable value begins with .).
Variable name (N): Path
Variable value (V): %JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;

4. Testing

Test whether the configuration is successful: click Start (or shortcut: Win+R) > Run (enter cmd) > OK (or press Enter), then enter the command javac and press Enter. If messages such as command parameters and syntax are displayed, the environment variables are configured successfully.

Linux

If openjdk is installed by using yum or apt-get command, the class library may be incomplete, thus leading to errors when you run relevant tools after the installation. Therefore, we recommend that you manually decompress and install JDK. Specific steps are as follows:

1. Download a JDK

Go to the Oracle website to download the desired JDK version to install.

Note：

The following uses jdk-8u151-linux-x64.tar.gz as an example. If you are using other versions, ensure that the extension is .tar.gz.

2. Create a directory

Run the following command to create the java directory in /usr/:

mkdir /usr/java
cd /usr/java 

Copy the downloaded jdk-8u151-linux-x64.tar.gz to the /usr/java/ directory.

3. Decompress the JDK

Run the following command to decompress the JDK:

tar -zxvf jdk-8u151-linux-x64.tar.gz 

4. Set environment variables

Edit the /etc/profile file. Add the following content to the profile file and save it:

set java environment
JAVA_HOME=/usr/java/jdk1.8.0_151        
JRE_HOME=/usr/java/jdk1.8.0_151/jre     
CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
export JAVA_HOME JRE_HOME CLASS_PATH PATH 

Note：

JAVA_HOME and JRE_HOME should be configured according to the actual installation paths and JDK version.

Run the following command for the modifications to take effect:

source /etc/profile 

5. Test

Run the following command to test the JDK installation:

java -version

If information about the Java version is displayed, the JDK is installed successfully.

java version "1.8.0_151"
Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)