CentOS安装JDK7
http://www.oracle.com/technetwork/java/javase/downloads/java-se-jdk-7-download-432154.html
1. 安装JDK1.7.0
[root@sea sea]# sudo rpm -ivh /home/sea/桌面/jdk-7-linux-i586.rpm

2. 设置环境变量
#rpm -ivh jdk-7-linux-i586.rpm
#vim /etc/profile

profile文件下面追加写入下面信息:
export JAVA_HOME=/usr/java/jdk1.7.0
export CLASSPATH=.:$JAVA_HOME/jre/lib/rt.jar:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export PATH=$PATH:$JAVA_HOME/bin

#source /etc/profile

3. 更新 alternatives，选择JDK版本
# update-alternatives --install /usr/bin/java java /usr/java/jdk1.7.0/bin/java 60

# update-alternatives --config java

Enter选择3