Install jdk under Linux (CentOS7)

Installing jdk under Linux is not the same as windows, it is a little more complicated, and record the installation process again

1. First, uninstall the built-in openJDK and files

1.1 Type in the terminal:

java -version

You can see the OpenJDK version information that comes with the system.

1.2 Type in the command window

rpm -qa | grep java

rpm	Management suite
-qa	Use query mode to query all packages
grep	Find the qualified string in the file
java	Find files containing java strings

These few of the above files can be deleted

java-1.8.0-openjdk-1.8.0.102-4.b14.el7.x86_64

java-1.8.0-openjdk-headless-1.8.0.102-4.b14.el7.x86_64

java-1.7.0-openjdk-headless-1.7.0.111-2.6.7.8.el7.x86_64
java-1.7.0-openjdk-1.7.0.111-2.6.7.8.el7.x86_64

noarch file can be deleted

javapackages-tools-3.4.1-11.el7.noarch
tzdata-java-2016g-2.el7.noarch
python-javapackages-3.4.1-11.el7.noarch

1.3 Type in the command window (permissions may not be enough, we can switch root, su root)

rpm -e --nodeps java-1.7.0-openjdk-1.7.0.111-2.6.7.8.el7.x86_64

For the complete delete file command, type in the command window:

rpm -e --nodeps java-1.7.0-openjdk-1.7.0.111-2.6.7.8.el7.x86_64
rpm -e --nodeps java-1.8.0-openjdk-1.8.0.102-4.b14.el7.x86_64
rpm -e --nodeps java-1.8.0-openjdk-headless-1.8.0.102-4.b14.el7.x86_64
rpm -e --nodeps java-1.7.0-openjdk-headless-1.7.0.111-2.6.7.8.el7.x86_64

The second step is to download the latest stable JDK

Official website: https://www.oracle.com/java/technologies/javase/javase-jdk8-downloads.html

Transfer the downloaded compressed package to Linux through xftp software

I transferred it to the /opt file of Linux

Unzip the compressed package of /opt

tar -xvzf  jdk-8u121-linux-x64.tar.gz

Enter the compressed file: save this /opt/jdk1.8_121

cd jdk1.8.0_121/

Edit in it, add some content

Save and exit: wq

Check if the installation is successful