Ubunto12.04 x64安装jdk1.7.0_75

1、下载jdk 64-bit版

在Oracle官网 http://www.oracle.com/technetwork/java/javase/downloads/index-jsp-138363.html?ssSourceSiteId=ocomen 下载 jdk-7u75-linux-x64.tar.gz 压缩包（因为我的系统是Ubunto，似乎只能下这个后缀的压缩包）

2、解压缩

将jdk-7u75-linux-x64.tar.gz拷贝到 /usr/lib/jvm/ 目录下面，这里如果没有jdk文件夹，则创建该文件夹,命令:

sudo mkdir jvm //创建文件夹jdk

sudo cp -r ~/download/jdk-7u75-linux-x64.tar.gz /usr/lib/jvm/ //把下载的文件拷贝到新创建的目录下面

sudo tar -zxvf jdk-7u45-linux-x64.tar.gz //解压缩文件，关于 tar 后面的指令，可以参考我的另一篇关于Linux常用指令的文章，里面有提到各个指令的区别。

3.设置环境变量

用nano打开/etc/profile文件

sudo nano /etc/profile

在文件的最后面增加：

export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_75

export JRE_HOME=/usr/lib/jvm/jdk1.7.0_75/jre

export PATH=$JAVA_HOME/bin:$JAVA_HOME/jre/bin:$PATH

export CLASSPATH=$CLASSPATH:.:$JAVA_HOME/lib:$JAVA_HOME/jre/lib

4.将系统默认的jdk修改过来
用update-alternatives工具来添加java可选配置项（这是一个dpkg的一个实用工具）。

$ sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_75/bin/java 300  //300 是优先级数值，随便用了一个

$ sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_75/bin/javac 300

$ sudo update-alternatives --config java

这时会出现类似于

$ sudo update-alternatives --config java  
There are 3 choices for the alternative java (providing /usr/bin/java).  
  
  Selection    Path                                            Priority   Status  
------------------------------------------------------------  
  0            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      auto mode  
  1            /usr/lib/jvm/jdk1.7.0_75/bin/java                300       manual mode  
  2            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      manual mode  
* 3            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1051      manual mode  
  
Press enter to keep the current choice[*], or type selection number: 1  //这里选择相应的号码  
update-alternatives: using /opt/jdk/jdk1.7.0_71/bin/java to provide /usr/bin/java (java) in manual mode  

$ sudo update-alternatives --config javac

$ sudo update-alternatives --config java  
There are 3 choices for the alternative javac (providing /usr/bin/javac).  
  
  Selection    Path                                            Priority   Status  
------------------------------------------------------------  
  0            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/javac   1061      auto mode  
  1            /usr/lib/jvm/jdk1.7.0_71/bin/javac                300       manual mode  
  2            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/javac   1061      manual mode  
* 3            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/javac   1051      manual mode  
  
Press enter to keep the current choice[*], or type selection number: 1  <span style="font-family: Arial, Helvetica, sans-serif;">//这里选择相应的号码</span>

update-alternatives: using /usr/lib/jvm/jdk1.7.0_75/bin/javac to provide /usr/bin/javac (javac) in manual mode  

5.检测

输入java -version

java version "1.7.0_75"
Java(TM) SE Runtime Environment (build 1.7.0_75-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.75-b04, mixed mode)

本篇文章参考于 Linux公社网站(www.linuxidc.com) 原文链接：http://www.linuxidc.com/Linux/2014-03/97475.htm