先下载，地址java7 http://www.oracle.com/technetwork/java/javase/downloads/java-archive-downloads-javase7-521261.htmljava8 http://www.oracle.com/technetwork/java/javase/downloads/java-archive-javase8-2177648.html在user建立目录并解压mkdir /usr/java && tar -zxvf jdk-7u79-linux-x64.tar.gz && mv jdk1.7.0_79 /usr/java/java7编辑/root目录下的.bashrc，在末尾添加export JAVA_HOME=/usr/java/java7export PATH=$PATH:$JAVA_HOME/binexport CLASSPATH=.:$JAVA_HOME/lib:$JAVA_HOME/jre/lib设置JDK java优先级update-alternatives --inst
