Ubuntu安裝JDK

一. Ubuntu 安裝JDK的兩種方式

1. 通過apt安裝.

2. 通過官網下載安裝包安裝.

這裏推薦第1種,因爲可以通過 apt-get upgrade 方式方便獲得jdk的升級

二. 通過apt安裝(jdk有很多版本, 這裏介紹兩種: openjdk和oracle的JDK)

1. openjdk

(1) 查找合適的openjdk版本:

apt-cache search openjdk

輸入以上命令後會列出很多版本, 選擇自己需要的即可:

default-jdk-doc - Standard Java or Java compatible Development Kit (documentation) 
…(省略部分顯示結果) 
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) 安裝

sudo apt-get install openjdk-8-jdk

(3) 配置環境變量, 編輯如下文件:

vim ~/.bashrc

在最後一行加:

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) 測試jdk是否安裝成功:

java -version

顯示如下結果, 則說明安裝成功:

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) 安裝oracle-java-installer

sudo apt-get install oracle-java8-installer

安裝器會提示你同意 oracle 的服務條款,選擇 ok, 然後選擇yes 即可

(3) 設置系統默認jdk

sudo update-java-alternatives -s java-8-oracle

(4) 如果即安裝了jdk7,又安裝了jdk8,要實現兩者的切換,可以:
jdk8 切換到jdk7

sudo update-java-alternatives -s java-7-oracle

jdk7 切換到jdk8

sudo update-java-alternatives -s java-8-oracle

(5) 測試jdk是否安裝成功:

java -version

三. 直接下載jdk壓縮包方式安裝

1. 官網下載JDK　　　

地址: http://www.oracle.com/technetwork/articles/javase/index-jsp-138363.html, 選擇相應的 .gz包下載

2. 解壓縮,放到指定目錄(以jdk-7u60-linux-x64.gz爲例)

創建目錄:

sudo mkdir /usr/lib/jvm

解壓縮到該目錄:

sudo tar -zxvf jdk-7u60-linux-x64.gz -C /usr/lib/jvm

3. 修改環境變量

sudo vim ~/.bashrc

文件的末尾追加下面內容:

#set oracle jdk environment
export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_60  ## 這裏要注意目錄要換成自己解壓的jdk 目錄
export JRE_HOME=${JAVA_HOME}/jre  
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  
export PATH=${JAVA_HOME}/bin:$PATH

使環境變量馬上生效:

source ~/.bashrc

4. 設置系統默認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

然後執行:

sudo update-alternatives --config java

若是初次安裝jdk,會有下面的提示 :

There is only one alternative in link group java (providing /usr/bin/java): 
/usr/lib/jvm/jdk1.7.0_60/bin/java

5. 測試jdk

java -version

若有如下結果, 則說明jdk 安裝成功:

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. 可能出現的錯誤信息

bash: ./java: cannot execute binary file

出現這個錯誤的原因可能是在32位的操作系統上安裝了64位的jdk, 查看你安裝的Ubuntu是32位還是64位系統:

sudo uname -m

i686表示是32位, x86_64表示是64位