執行個體場景應用（sun JDK1.7和sun JDK1.8切換alternatives）echo export PATH=$PATH:$JAVA_HOME/bin >>~/.bash_profile

Java運用于執行java程式（java運作環境）

Javac運用于java程式編譯（java程式開發環境）

步驟二：alternatives安裝JDK

#alternatives --install /usr/bin/java java /usr/local/jdk版本/bin/java 1

#alternatives --install /usr/bin/javac java /usr/local/jdk版本/bin/javac 2

步驟二：檢視可用的版本資訊

#alternatives --display java

#alternatives --display javac

步驟三：切換java版本

#alternatives --config java

#alternatives --config javac

删除jdk版本（可選項，需要删除時使用--remove）

#alternatives --remove java /usr/local/java/jdk版本/bin

#alternatives --remove javac /usr/local/java/jdk版本/bin

步驟四：修改目前使用者的jdk運作環境

#echo export JAVA_HOME=/usr/bin/java >>~/.bash_profile

echo export PATH=$PATH:$JAVA_HOME/bin >>~/.bash_profile

# source ~/.bash_profile           

注意需要注釋掉/etc/profile檔案裡面的JAVA_HOM

檢視及管理JAVA_HOME

echo $JAVA_HOME

/usr/local/jdk

java -version

java version "1.8.0_111"

Java(TM) SE Runtime Environment (build 1.8.0_111-b14)

Java HotSpot(TM) 64-Bit Server VM (build 25.111-b14, mixed mode)

#執行個體     [cqs@centos7 jdk]$echo ’export JAVA_HOME=/usr/bin/java’ >>~/.bash_profile     [cqs@centos7 jdk]$ echo ‘export PATH=$PATH:$JAVA_HOME/bin’ >>~/.bash_profile     [cqs@centos7 jdk]$ source ~/.bash_profile           

[cqs@centos7 jdk]$ echo $JAVA_HOME           

/usr/bin/java

[cqs@centos7 jdk]$ echo $PATH           

/usr/local/bin:/usr/bin:/usr/local/mysql/bin:/usr/local/sbin:/usr/sbin:/home/cqs/.local/bin:/home/cqs/bin:/usr/bin/java/bin

步驟一：alternatives安裝JDK1.7(連結路徑【link】:/usr/bin/java  連結名【name】:java 應用程式JAVA實際路徑【path】：/home/cqs/data/jdk/jdk1.7.0_80/bin/java  優先級【priority】 :1)         [cqs@centos7 jdk]$ sudo alternatives --install /usr/bin/java java ~/data/jdk/jdk1.7.0_80/bin/java 1         [cqs@centos7 jdk]$ sudo alternatives --config java           

There is 1 program that provides 'java'.

Selection Command

*+ 1 /home/cqs/data/jdk/jdk1.7.0_80/bin/java

Enter to keep the current selection[+], or type selection number:

[cqs@centos7 jdk]$ java -version           

java version "

1.7.0_80"

Java(TM) SE Runtime Environment (build 1.7.0_80-b15)

Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)

alternatives安裝JDK1.8

[cqs@centos7 jdk]$ sudo alternatives --install /usr/bin/java java ~/data/jdk/jdk1.8.0_161/bin/java 2     [cqs@centos7 jdk]$ sudo alternatives --config java           

There are 2 programs which provide 'java'.

• 1 /home/cqs/data/jdk/jdk1.7.0_80/bin/java

  • 2 /home/cqs/data/jdk/jdk1.8.0_161/bin/java

    Enter to keep the current selection[+], or type selection number: 2

  [cqs@centos7 jdk]$ java -version

  java version "1.8.0_161"

  Java(TM) SE Runtime Environment (build 1.8.0_161-b12)

  Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)

  [cqs@centos7 jdk]$ sudo alternatives --config java

  *+ 2 /home/cqs/data/jdk/jdk1.8.0_161/bin/java

  Enter to keep the current selection[+], or type selection number: 1

  java version "1.7.0_80"