Introduction
Java is a programming technology originally developed by Sun Microsystems and later acquired by Oracle. Oracle Java is a proprietary implementation for Java that is free to download and use for commercial use, but not to redistribute, therefore it is not included in a officially maintained repository.
There are many reasons why you would want to install Oracle Java over OpenJDK. In this tutorial, we will not discuss the differences between the above mentioned implementations.
Assumptions
This tutorial assumes that you have an account with DigitalOcean, as well as a Droplet running Debian 7 or Ubuntu 12.04 or above. You will need root privileges (via sudo) to complete the tutorial.
You will need to know whether you are running a 32 bit or a 64 bit OS:
uname -m
- x86_64: 64 bit kernel
- i686: 32 bit kernel
Downloading Oracle Java JDK
Using your web browser, go to the Oracle Java SE (Standard Edition) website and decide which version you want to install:
- JDK: Java Development Kit. Includes a complete JRE plus tools for developing, debugging, and monitoring Java applications.
- Server JRE: Java Runtime Environment. For deploying Java applications on servers. Includes tools for JVM monitoring and tools commonly required for server applications.
In this tutorial we will be installing the JDK Java SE Development Kit 8 x64 bits. Accept the license and copy the download link into your clipboard. Remember to choose the right tar.gz (64 or 32 bits). Use wget to download the archive into your server:
wget --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u5-b13/jdk-8u5-linux-x64.tar.gz
Oracle does not allow downloads without accepting their license, therefore we needed to modify the header of our request. Alternatively, you can just download the compressed file using your browser and manually upload it using a SFTP/FTP client.
Always get the latest version from Oracle‘s website and modify the commands from this tutorial accordingly to your downloaded file.
Installing Oracle JDK
In this section, you will need sudo privileges:
sudo su
The /opt directory is reserved for all the software and add-on packages that are not part of the default installation. Create a directory for your JDK installation:
mkdir /opt/jdk
and extract java into the /opt/jdk directory:
tar -zxf jdk-8u5-linux-x64.tar.gz -C /opt/jdk
Verify that the file has been extracted into the /opt/jdk directory.
ls /opt/jdk
Setting Oracle JDK as the default JVM
In our case, the java executable is located under /opt/jdk/jdk1.8.0_05/bin/java . To set it as the default JVM in your machine run:
update-alternatives --install /usr/bin/java java /opt/jdk/jdk1.8.0_05/bin/java 100
and
update-alternatives --install /usr/bin/javac javac /opt/jdk/jdk1.8.0_05/bin/javac 100
Verify your installation
Verify that java has been successfully configured by running:
update-alternatives --display java
and
update-alternatives --display javac
The output should look like this:
java - auto mode
link currently points to /opt/jdk/jdk1.8.0_05/bin/java
/opt/jdk/jdk1.8.0_05/bin/java - priority 100
Current ‘best‘ version is ‘/opt/jdk/jdk1.8.0_05/bin/java‘.
javac - auto mode
link currently points to /opt/jdk/jdk1.8.0_05/bin/javac
/opt/jdk/jdk1.8.0_05/bin/javac - priority 100
Current ‘best‘ version is ‘/opt/jdk/jdk1.8.0_05/bin/javac‘.
Another easy way to check your installation is:
java -version
The output should look like this:
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)ubuntu vps 安装java