Introduction

As a lot of articles and programs require to have Java installed, this article will guide you through the process of installing and managing different versions of Java.

 

Installing default JRE/JDK

This is the recommended and easiest option. This will install OpenJDK 6 on Ubuntu 12.04 and earlier and on 12.10+ it will install OpenJDK 7.

Installing Java with apt-get is easy. First, update the package index:

sudo apt-get update

Then, check if Java is not already installed:

java -version

If it returns "The program java can be found in the following packages", Java hasn't been installed yet, so execute the following command:

sudo apt-get install default-jre

This will install the Java Runtime Environment (JRE). If you instead need the Java Development Kit (JDK), which is usually needed to compile Java applications (for example Apache AntApache MavenEclipseand IntelliJ IDEA execute the following command:

sudo apt-get install default-jdk

That is everything that is needed to install Java.

All other steps are optional and must only be executed when needed.

 

Installing OpenJDK 7 (optional)

To install OpenJDK 7, execute the following command:

sudo apt-get install openjdk-7-jre

This will install the Java Runtime Environment (JRE). If you instead need the Java Development Kit (JDK), execute the following command:

sudo apt-get install openjdk-7-jdk
 

Installing Oracle JDK (optional)

The Oracle JDK is the official JDK; however, it is no longer provided by Oracle as a default installation for Ubuntu.

You can still install it using apt-get. To install any version, first execute the following commands:

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update

Then, depending on the version you want to install, execute one of the following commands:

Oracle JDK 6

This is an old version but still in use.

sudo apt-get install oracle-java6-installer

Oracle JDK 7

This is the latest stable version.

sudo apt-get install oracle-java7-installer

Oracle JDK 8

This is a developer preview, the general release is scheduled for March 2014. This external article about Java 8 may help you to understand what it's all about.

sudo apt-get install oracle-java8-installer
 

Managing Java (optional)

When there are multiple Java installations on your Droplet, the Java version to use as default can be chosen. To do this, execute the following command:

sudo update-alternatives --config java

It will usually return something like this if you have 2 installations (if you have more, it will of course return more):

There are 2 choices for the alternative java (providing /usr/bin/java).

Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0 /usr/lib/jvm/java-7-oracle/jre/bin/java 1062 auto mode
1 /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java 1061 manual mode
2 /usr/lib/jvm/java-7-oracle/jre/bin/java 1062 manual mode Press enter to keep the current choice[*], or type selection number:

You can now choose the number to use as default. This can also be done for the Java compiler (javac):

sudo update-alternatives --config javac

It is the same selection screen as the previous command and should be used in the same way. This command can be executed for all other commands which have different installations. In Java, this includes but is not limited to: keytooljavadoc and jarsigner.

 

Setting the "JAVA_HOME" environment variable

To set the JAVA_HOME environment variable, which is needed for some programs, first find out the path of your Java installation:

sudo update-alternatives --config java

It returns something like:

There are 2 choices for the alternative java (providing /usr/bin/java).

Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0 /usr/lib/jvm/java-7-oracle/jre/bin/java 1062 auto mode
1 /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java 1061 manual mode
2 /usr/lib/jvm/java-7-oracle/jre/bin/java 1062 manual mode Press enter to keep the current choice[*], or type selection number:

The path of the installation is for each:

  1. /usr/lib/jvm/java-7-oracle

  2. /usr/lib/jvm/java-6-openjdk-amd64

  3. /usr/lib/jvm/java-7-oracle

Copy the path from your preferred installation and then edit the file /etc/environment:

sudo nano /etc/environment

In this file, add the following line (replacing YOUR_PATH by the just copied path):

JAVA_HOME="YOUR_PATH"

Or:

export JAVA_HOME=/usr/lib/jvm/default-java/

That should be enough to set the environment variable. Now reload this file:

source /etc/environment

Test it by executing:

echo $JAVA_HOME

If it returns the just set path, the environment variable has been set successfully. If it doesn't, please make sure you followed all steps correctly.

Submitted by: Koen Vlaswinkel

Install Java JDK JRE on Ubuntu/Debian with Apt-Get的更多相关文章

  1. How to Install JAVA 8 (JDK/JRE 8u111) on Debian 8 & 7 via PPA

    Oracle JAVA 8 Stable release has been released on Mar,18 2014 and available to download and install. ...

  2. Install Oracle Java JDK/JRE 7u55 on Fedora 20/19, CentOS/RHEL 6.5/5.10

    What’s new in Sun/Oracle Java 7 VM Compressed 64-bit object pointers Garbage-First GC (G1) JSR 292: ...

  3. JAVA(JDK,JRE)更改目录安装及环境变量配置

    重温一下 JAVA(JDK,JRE)更改目录安装及环境变量配置 https://jingyan.baidu.com/article/e2284b2b5b7ae5e2e7118d11.html 备注:随 ...

  4. How To Install Java with Apt-Get on Ubuntu 16.04

    Introduction Java and the JVM (Java's virtual machine) are widely used and required for many kinds o ...

  5. linux查看java jdk jre安装路径和设置环境变量

    一. 查看java jdk安装路径和设置环境变量 windows: set java_home:查看JDK安装路径 java -version:查看JDK版本 linux: whereis java ...

  6. Ubuntu 18.04 Java JDK/JRE 安装命令

    安装默认版本 sudo apt install default-jdk Java 8 sudo apt install openjdk-8-jdk 如果我们在服务器上安装了多个Java版本,我们可以使 ...

  7. java jdk jre

    Java11新特性: https://www.cnblogs.com/eric-shao/p/10025180.html java的一些基本概念——java11.jdk.jre.jvm: https: ...

  8. rhel install java jdk

    Linux安装JDK完整步骤 1.检查一下系统中的jdk版本 [root@localhost software]# java -version 显示: openjdk version "1. ...

  9. JAVA -- JDK JRE JAR

    转载:http://blog.csdn.net/wym19830218/article/details/5399401 JDK里面的工具也是用JAVA编写的,它们本身运行的时候也需要一套JRE,如C: ...

随机推荐

  1. 网络基础 04_IP编址

    1 IP地址简介 什么是IP地址 在IP网络中,任何一个节点都需要一个唯一的IP IPV4 :32位 点分十进制 2 IP编址分类 有类编址 IP地址的类别 IP地址类型 网络地址:指代网络的地址.在 ...

  2. 简单工厂模式&策略模式-简介与区别

    不得不说,这两种模式真的很像. 相似点:都用到了面向对象的继承.多态.抽象,都拥有相似的结构. 不同点:工厂模式仅提供具体的实例对象,怎么使用这个对象是client的自由,策略模式client可以通过 ...

  3. 思科设备配置DHCP服务

    路由器,三层交换机都是可以做DHCP服务的,下面以Cisco 3750G-24TS-S为例配置DHCP服务,指令如下: ip dhcp pool DHCP-Server network 192.168 ...

  4. dubbo学习笔记:快速搭建

    搭建一个简单的dubbo服务 参考地址: dubbo官网:http://dubbo.apache.org/zh-cn/docs/user/references/registry/zookeeper.h ...

  5. lambda modern C++

    Lambda expressions (since C++11) Syntax   [ captures ] <tparams>(optional)(c++20) ( params ) s ...

  6. 什么是O/RMapping?为什么要用O/R Mapping?

    什么是O/R Mapping ? O/R Mapping 就是有一大堆的类库,我们调用它的时候用面向对象的方式来调,它帮我们翻译成为面向关系的方式. 为什么要用O/R Mapping? 我们编程会更加 ...

  7. 第一个hibernate程序HelloWorldHibernate

    HelloWorldHibernate步骤: HelloWorld 1,新建java项目hibernate_0100_HelloWorld 2,学习User-library-hibernate,并加入 ...

  8. 爱奇艺视频显示列表CSS实现

    css: body{margin:0;font-size: 12px;font-family: "宋体":} ul{margin:0;padding:0;list-style: n ...

  9. Java网络编程(二)关于Socket的一些个人想法

    1.Socket之间是如何通信的? 1.1 通信是要两两之间进行的所以应该有至少一个客户端(Client)和一个服务器端(Server),一般来说都是多个c端对一个s端---c\s 1.2 在客户端: ...

  10. 【LeetCode题解】144_二叉树的前序遍历

    目录 [LeetCode题解]144_二叉树的前序遍历 描述 方法一:递归 Java 代码 Python 代码 方法二:非递归(使用栈) Java 代码 Python 代码 [LeetCode题解]1 ...