系统被来就有openjdk，但是开发工具需要sun的jdk,于是下载一个压缩包并解压到一个位置。使用alternative命令切换
alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_79/jre/bin/java 20000 alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.7.0_79/jre/bin/javaws 20000 alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_79/jre/bin/javac 20000 alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.7.0_79/jre/bin/jar 20000
然后就是
alternatives --config java