[font=Book Antiqua][color=#010101]最近想在ubuntu上安装oracle 12c，首先安装了jdk7。
[font=Book Antiqua][color=#010101]1. [color=#010101]创建 [font=Book Antiqua][color=#010101]jdk[color=#010101]安装路径：[font=Book Antiqua][color=#010101]/usr/lib/jdk
[color=#111]cd /usr/lib
[color=rgb(1, 1, 1)]sudo mkdir jdk
[color=rgb(1, 1, 1)]

[font=Book Antiqua][color=#010101]2. [color=#010101]下载 [font=Book Antiqua][color=#010101]jdk

[font=Book Antiqua][color=#010101]3. [color=#010101]安装 [font=Book Antiqua][color=#010101]jdk
[color=rgb(1, 1, 1)]sudo tar xzvf ./Downloads/jdk-7u71-linux-x64.tar.gz -C /usr/lib/jdk
[font=Book Antiqua][color=#010101]x : [color=#010101]从 [font=Book Antiqua][color=#010101]tar [color=#010101]包中把文件提取出来
[font=Book Antiqua][color=#010101]z : [color=#010101]表示 [font=Book Antiqua][color=#010101]tar [color=#010101]包是被 [font=Book Antiqua][color=#010101]gzip [color=#010101]压缩过的，所以解压时需要用 [font=Book Antiqua][color=#010101]gunzip [color=#010101]解压[font=Book Antiqua][color=#010101]
v : [color=#010101]显示详细信息 [font=Book Antiqua][color=#010101]
f xxx.tar.gz : [color=#010101]指定被处理的文件是 [font=Book Antiqua][color=#010101]xxx.tar.gz
[font=Book Antiqua][color=#010101]

[font=Book Antiqua][color=#010101]4. [color=#010101]配置环境变量
gedit[color=#111] ~/.bashrc （或者vim文本编辑器）
exprot JAVA_HOME=/usr/lib/jdk/jdk1.7.0_71
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
exxport PATH=${JAVA_HOME}/bin:$PATH

5. 配置默认JDK版本
[backcolor=rgb(243, 245, 252)][size=14px]sudo update-alternatives --install /usr/bin/java java /usr/lib/jdk/jdk1.7.0_71[backcolor=rgb(243, 245, 252)][size=14px]/bin/java 300
[backcolor=rgb(243, 245, 252)][size=14px]sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jdk/jdk1.7.0_71[backcolor=rgb(243, 245, 252)][size=14px]/bin/javac 300
[backcolor=rgb(243, 245, 252)][size=14px]sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jdk/jdk1.7.0_71[backcolor=rgb(243, 245, 252)][size=14px]/bin/jar 300
[backcolor=rgb(243, 245, 252)][size=14px]sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jdk/jdk1.7.0_71[backcolor=rgb(243, 245, 252)][size=14px]/bin/javah 300
[backcolor=rgb(243, 245, 252)][size=14px]sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jdk/jdk1.7.0_71[backcolor=rgb(243, 245, 252)][size=14px]/bin/javap 300
[backcolor=rgb(243, 245, 252)][size=14px]

[backcolor=rgb(247, 252, 255)][font=Arial, 宋体][size=14px]执行 sudo update-alternatives --config java
[backcolor=rgb(247, 252, 255)][font=Arial, 宋体]若是初次安装 JDK， 将提示There is only one alternative in link group java (providing /usr/bin/java): /usr/lib/jvm/java/bin/java无需配置。
[backcolor=rgb(247, 252, 255)][font=Arial, 宋体]若是非初次安装，将有不同版本的 JDK 选项。[backcolor=rgb(247, 252, 255)][font=Arial, 宋体][size=14px]

[backcolor=rgb(247, 252, 255)][font=Arial, 宋体][size=14px]6. 测试JDK是否安装成功
[font=Arial, 宋体][size=14px]java -version