ubuntu install install JDK

1. Prerequisite preparation:

　　下载JDK：http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

2. Install JDk:

1. First open the terminal, enter the download directory and unzip it to the current directory:
    tar -zxvf jdk-8u171-linux-i586.tar.gz #Modify according to the file you downloaded 

2. Move the decompressed file to where you want to put it: 
　　sudo mv jdk1.8.0_171 /opt/jdk #here I moved it to /opt/jdk 
3. Configure environment variables: 
　　sudo vi ~/.bashrc #The global variables are configured here 
　　Add the following code to the end of the file: 
　　　　export JAVA_HOME=/opt/jdk/jdk1.8.0_171 # Add the moved JDK path after JAVA_HOME= 
　　　　export JRE_HOME=${JAVA_HOME}/jre   
　　　　export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib   
　　　　export PATH=${JAVA_HOME}/bin:$PATH 


　　　　　　###/etc/profile ~/.profile /etc/bashrc ~/.bashrc The difference between the four:

　　　　　　　　　/etc/profile is prepared for each user of the system. If you want to set it for each user of the machine, you can set it in /etc/profile uniformly.

　　　　　　　　　~/.profile is the settings file for a single user.

　　　　　　　　　/etc/bashrc is the settings file for all bash shell users

　　　　　　　　　~/.bashrc is the system settings file for a single user.

4. Start the /.bashrc file: 
　　source ~/.bashrc 
5. Check the Java version: 
　　java -version 
　　　　If the Java version number appears, the installation is successful!

 ###Newbie, please correct me