ubuntu 15.04 安装配置 JDK1.8

http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

 sudo mkdir /usr/lib/jvm
 sudo tar zxvf jdk-8u45-linux-x64.tar.gz -C /usr/lib/jvm
 cd /usr/lib/jvm
 sudo mv jdk1.8.0_45 java

$ sudo gedit ~/.bashrc

export JAVA_HOME=/usr/lib/jvm/java 
export JRE_HOME=${JAVA_HOME}/jre  
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  
export PATH=${JAVA_HOME}/bin:$PATH  

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/java/bin/java 300  
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/java/bin/javac 300  
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/java/bin/jar 300   
sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/java/bin/javah 300   
sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/java/bin/javap 300   

sudo update-alternatives --config java

There is only one alternative in link group java (providing /usr/bin/java): /usr/lib/jvm/java/bin/java
无需配置。

有 2 个候选项可用于替换 java (提供 /usr/bin/java)。

选择 路径 优先级 状态
------------------------------------------------------------
* 0 /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java 1071 自动模式
1 /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java 1071 手动模式
2 /usr/lib/jvm/java/bin/java 300 手动模式

要维持当前值[*]请按回车键，或者键入选择的编号：

$ java -version

出现

java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

安装成功！