一. Ubuntu 安装JDK的两种方式
1. 通过apt安装.
2. 通过官网下载安装包安装.
这里推荐第1种,因为可以通过 apt-get upgrade 方式方便获得jdk的升级
二. 通过apt安装(jdk有很多版本, 这里介绍两种: openjdk和oracle的JDK)
1. openjdk
(1) 查找合适的openjdk版本:
apt-cache search openjdk
输入以上命令后会列出很多版本, 选择自己需要的即可:
default-jdk-doc - Standard Java or Java compatible Development Kit (documentation)
…(省略部分显示结果)
openjdk-6-source - OpenJDK Development Kit (JDK) source files
openjdk-7-jre-dcevm - Alternative VM for OpenJDK 7 with enhanced class redefinition
openjdk-7-jre-lib - OpenJDK Java runtime (architecture independent libraries)
openjdk-7-jre-zero - Alternative JVM for OpenJDK, using Zero/Shark
openjdk-8-dbg - Java runtime based on OpenJDK (debugging symbols)
openjdk-8-demo - Java runtime based on OpenJDK (demos and examples)
openjdk-8-doc - OpenJDK Development Kit (JDK) documentation
openjdk-8-jdk - OpenJDK Development Kit (JDK)
openjdk-8-jre - OpenJDK Java runtime, using Hotspot JIT
openjdk-8-jre-headless - OpenJDK Java runtime, using Hotspot JIT (headless)
openjdk-8-jre-jamvm - Alternative JVM for OpenJDK, using JamVM
openjdk-8-jre-zero - Alternative JVM for OpenJDK, using Zero/Shark
openjdk-8-source - OpenJDK Development Kit (JDK) source files
uwsgi-app-integration-plugins - plugins for integration of uWSGI and application
uwsgi-plugin-jvm-openjdk-7 - Java plugin for uWSGI (OpenJDK 7)
(2) 安装
sudo apt-get install openjdk-8-jdk
(3) 配置环境变量, 编辑如下文件:
vim ~/.bashrc
在最后一行加:
export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64
export PATH=$JAVA_HOME/bin:$PATH
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
(4) 测试jdk是否安装成功:
java -version
显示如下结果, 则说明安装成功:
openjdk version “1.8.0_91”
OpenJDK Runtime Environment (build 1.8.0_91-8u91-b14-0ubuntu4~15.10.1-b14)
OpenJDK Server VM (build 25.91-b14, mixed mode)
2. oracle的JDK
(1) 添加ppa
sudo apt install software-properties-common
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
(2) 安装oracle-java-installer
sudo apt-get install oracle-java8-installer
安装器会提示你同意 oracle 的服务条款,选择 ok, 然后选择yes 即可
(3) 设置系统默认jdk
sudo update-java-alternatives -s java-8-oracle
(4) 如果即安装了jdk7,又安装了jdk8,要实现两者的切换,可以:
jdk8 切换到jdk7
sudo update-java-alternatives -s java-7-oracle
jdk7 切换到jdk8
sudo update-java-alternatives -s java-8-oracle
(5) 测试jdk是否安装成功:
java -version
三. 直接下载jdk压缩包方式安装
1. 官网下载JDK
地址: http://www.oracle.com/technetwork/articles/javase/index-jsp-138363.html, 选择相应的 .gz包下载
2. 解压缩,放到指定目录(以jdk-7u60-linux-x64.gz为例)
创建目录:
sudo mkdir /usr/lib/jvm
解压缩到该目录:
sudo tar -zxvf jdk-7u60-linux-x64.gz -C /usr/lib/jvm
3. 修改环境变量
sudo vim ~/.bashrc
文件的末尾追加下面内容:
#set oracle jdk environment
export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_60 ## 这里要注意目录要换成自己解压的jdk 目录
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH
使环境变量马上生效:
source ~/.bashrc
4. 设置系统默认jdk版本
sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_60/bin/java 300
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_60/bin/javac 300
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.7.0_60/bin/jar 300
sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk1.7.0_60/bin/javah 300
sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.7.0_60/bin/javap 300
然后执行:
sudo update-alternatives --config java
若是初次安装jdk,会有下面的提示 :
There is only one alternative in link group java (providing /usr/bin/java):
/usr/lib/jvm/jdk1.7.0_60/bin/java
5. 测试jdk
java -version
若有如下结果, 则说明jdk 安装成功:
java version "1.7.0_60"
Java(TM) SE Runtime Environment (build 1.7.0_60-b19)
Java HotSpot(TM) 64-Bit Server VM (build 24.60-b09, mixed mode)
6. 可能出现的错误信息
bash: ./java: cannot execute binary file
出现这个错误的原因可能是在32位的操作系统上安装了64位的jdk, 查看你安装的Ubuntu是32位还是64位系统:
sudo uname -m
i686表示是32位, x86_64表示是64位
