一.jdk1.8安装

1. 从网站上下载jdk1.8包(jdk-8u73-linux-x64.tar.gz )

2.解压到 /usr/java/目录下，

解压安装到：

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tar zxvf jdk-8u73-linux-x64.tar.gz  -C /usr/java/

ln -s /usr/java/jdk1.8.0_73  /usr/java/jdk

3.环境变量配置：

(/etc/profile文件中添加：)

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vi  /etc/profile
JAVA_HOME=/usr/java/jdk
PATH=$PATH:$JAVA_HOME/bin:$JAVA_HOME/jre/bin
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export JAVA_HOME PATH CLASSPATH

添加完毕保存退出

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source /etc/profile
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sudo update-alternatives --install /usr/bin/java java /usr/java/jdk/bin/java 300
sudo update-alternatives --install /usr/bin/javac javac /usr/java/jdk/bin/javac 300
sudo update-alternatives  --install  /usr/bin/jar jar /usr/java/jdk/bin/jar 300
sudo update-alternatives  --install  /usr/bin/javah javah /usr/java/jdk/bin/javah 300
sudo update-alternatives  --install  /usr/bin/javap javap /usr/java/jdk/bin/javap 300
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java -version

显示
java version “1.8.0_73”
Java(TM) SE Runtime Environment (build 1.8.0_73-b02)
Java HotSpot(TM) 64-Bit Server VM (build 25.73-b02, mixed mode)