linux安装配置java，及修改默认java

修改classpath:

vim /etc/profile

export JAVA_HOME=/usr/share/java7
export JRE_HOME=$JAVA_HOME/jre
export CLASSPATH=.:$JAVA_HOME/lib:$JRE_HOME/lib:$CLASSPATH
export PATH=$JAVA_HOME/bin:$PATH

Ubuntu系统默认安装并使用OpenJDK(usr/lib/jvm/)，因此需要手动修改系统默认的JDK:

sudo update-alternatives --install /usr/bin/javac javac /usr/lib/java/jdk1.7.0_11/bin/javac 300

sudo update-alternatives --install /usr/bin/java java /usr/lib/java/jdk1.7.0_11/bin/java 300

sudo update-alternatives --config javac

sudo update-alternatives --config java