jdk下载地址
我把jdk安装到/opt/java，，所以在Terminal窗口里执行下面的代码:
sudo mkdir /opt/java
sudo tar zxvf jdk-7-linux-i586.tar.gz -C/opt/java
1. 用编辑器打开 /etc/environment
gedit /etc/environment
2. 修改文件
PATH=”/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:usr/games:${JAVA_HOME}/bin”
JAVA_HOME=/opt/java/jdk1.7.0
JRE_HOME=${JAVA_HOME}/jre
CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib”
3.打开bashrc文件
sudo gedit ~/.bashrc
4.添加如下代码
export JAVA_HOME=/opt/java/jdk1.7.0
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH
5. 重新加载bashrc
source ~/.bashrc
6. 配置默认JDK版本：由于Ubuntu中可能会有默认的JDK，如openjdk，所以，为了将我们安装的JDK设置为默认JDK版本，还要进行下面的配置：
sudo update-alternatives –install /usr/bin/java java /opt/java/jdk1.7.0/bin/java 300
sudo update-alternatives –install /usr/bin/javac javac /opt/java/jdk1.7.0/bin/javac 300
sudo update-alternatives –install /usr/bin/jar jar /opt/java/jdk1.7.0/bin/jar 300
sudo update-alternatives –install /usr/bin/javah javah /opt/java/jdk1.7.0/bin/javah 300
sudo update-alternatives –install /usr/bin/javap javap /opt/java/jdk1.7.0/bin/javap 300
7.然后执行：
sudo update-alternatives –config java
sudo update-alternatives –config javac
sudo update-alternatives –config jar
8.检测环境是否配好
java -version
java version “1.7.0”
Java(TM) SE Runtime Environment (build 1.7.0-b147)
Java HotSpot(TM) Server VM (build 21.0-b17, mixed mode)
对于旅行，从来都记忆模糊。记不得都去了哪些地方，
