安装Java

1. 下载最新的JAVA JDK

百度Java进入Oracle官网下载

2. 解压缩文件并移动至/opt

tar -xzvf jdk-8u162-linux-x64.tar.gz

mv jdk1.8.0_162 /opt

cd /opt/jdk1.8.0_162

3. 设置环境变量

1）执行 gedit ~/.bashrc ， 并添加下列内容

# install JAVA JDK

export JAVA_HOME=/opt/jdk1.8.0_162

export CLASSPATH=.:${JAVA_HOME}/lib

export PATH=${JAVA_HOME}/bin:$PATH

2）执行 source ~/.bashrc

4. 安装并注册

执行（分别对应java、javac和浏览器插件的安装与注册）：

update-alternatives --install /usr/bin/java java /opt/jdk1.8.0_162/bin/java 1

update-alternatives --install /usr/bin/javac javac /opt/jdk1.8.0_162/bin/javac 1

update-alternatives --install /usr/lib/mozilla/plugins/libjavaplugin.so mozilla-javaplugin.so /opt/jdk1.7.0_162/jre/lib/amd64/libnpjp2.so 1

update-alternatives --set java /opt/jdk1.8.0_91/bin/java

update-alternatives --set javac /opt/jdk1.8.0_91/bin/javac

update-alternatives --set mozilla-javaplugin.so /opt/jdk1.7.0_45/jre/lib/amd64/libnpjp2.so

查看结果：

update-alternatives --config java

update-alternatives --config javac

5. 测试

java -version

#output
java version "1.8.0_162"
Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)