1. Win7 configuration

First, download the JDK that matches your operating system version, for example, the latest JDK 8:

Download link:http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html；

Of course, most developers do not use the latest JDK. The current mainstream choices are JDK 6 and JDK 7, and of course more and more developers are switching to the JDK 8 platform.

After downloading, install it all the way through. The local JDK installation path isC:\Program Files\Java\jdk1.7.0_79

Then follow these steps: Computer --> Properties --> Advanced System Settings --> Environment Variables

In the environment variables for xxx (xxx represents your computer name), create a new JAVA_HOME (this name can be customized, but this is the common one), and enter the value

As shown in the figure.

Step 2: In the system variables below, find Path, edit it, and add at the very end:

%JAVA_HOME%\bin;%JAVA_HOME%\jre\bin

As shown:

Then create a new variable named CLASSPATH, and enter the value .;%JAVA_HOME%\lib;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\lib\tools.jar, note the dot!!!

Click OK.Windows key + R, enter cmd

Then enter the commandjava -versionIf you can see the Java version information, it means the Java environment variable configuration was successful.

2. Linux environment variable configuration

Both Linux and Win7 are multi-user operating systems, so the location where environment variables are configured determines the scope within which the environment variables take effect.

As above, under Win7 I configured it under the user "bai", so only when the user "bai" logs in can the Java environment be used. Other users cannot use it. Of course, if your configuration is in the system variables, then all users on this computer can use this environment. Once you are familiar with this concept, configuring environment variables on Linux becomes simple.

Step 1: Download

Download the JDK version corresponding to Linux to /usr/local, then extract it:

$ wget http://download.oracle.com/otn-pub/java/jdk/7u79-b15/jdk-7u79-linux-x64.tar.gz
$ tar -zxvf jdk-8u66-linux-x64.tar.gz
$ mv jdk1.7.0_79 jdk1.7          # 重命名

Get the JDK directory path /usr/local/jdk1.7

Step 2: Configure the Java environment for all users

Log in as the root user and run vim /etc/profile

Press the Insert key, then move to the last line and add

#configuration java development enviroument
export JAVA_HOME=/usr/local/jdk1.7
export PATH=$JAVA_HOME/bin:$PATH 
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar 

Then press the Esc key, enter wq, and after exiting, enterjava -versionIf you can see the corresponding version information, it means the Java environment variable configuration was successful.

Step 3: Configure the Java environment for the current user

vim ~/.bash_profile file

Similarly, add the following information:

#configuration java development enviroument
export JAVA_HOME=/usr/local/jdk1.7
export PATH=$JAVA_HOME/bin:$PATH 
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar 

Reload the system configuration file:

source /etc/profile

Check whether the JDK was installed successfully:

java -version