jdk檔案下載

連結：https://pan.baidu.com/s/1GiNrIiVhIJzfTEIXtcEYuw
提取碼：j6ad
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伺服器新建jvm資料夾

把下載的壓縮包放上傳這裡面進行解壓 ：tar -zxvf jdk-11.0.8_linux-x64_bin.tar.gz

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_60/bin/java 300  
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_60/bin/javac 300  
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.7.0_60/bin/jar 300   
sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk1.7.0_60/bin/javah 300   
sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.7.0_60/bin/javap 300

修改環境變數

sudo vim ~/.bashrc

在末尾追加以下內容

#set oracle jdk environment
export JAVA_HOME=/usr/lib/jvm/jdk-11.0.8  ## 這裡要注意目錄要換成自己解壓的jdk 目錄
export JRE_HOME=${JAVA_HOME}/jre  
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  
export PATH=${JAVA_HOME}/bin:$PATH  

使環境變數馬上生效

 source ~/.bashrc

設定系統預設jdk版本

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk-11.0.8/bin/java 300
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk-11.0.8/bin/javac 300
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk-11.0.8/bin/jar 300
sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk-11.0.8/bin/javah 300
sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk-11.0.8/bin/javap 300

　　然後執行

sudo update-alternatives --config java

若是初次安裝jdk,會有下面的提示

There is only one alternative in link group java (providing /usr/bin/java):
/usr/lib/jvm/jdk1.7.0_60/bin/java

　否者,選擇合適的jdk

檢視是否安裝

java -version