實例場景應用（sun JDK1.7和sun JDK1.8切換alternatives）

Java運用于執行java程序（java運行環境）
Javac運用于java程序編譯（java程序開發環境）
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：查看可用的版本信息
#alternatives --display java
#alternatives --display javac
步驟三：切換java版本
#alternatives --config java
#alternatives --config javac
刪除jdk版本（可選項，需要刪除時使用--remove）
#alternatives --remove java /usr/local/java/jdk版本/bin
#alternatives --remove javac /usr/local/java/jdk版本/bin
步驟四：修改當前用戶的jdk運行環境
#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文件里面的JAVA_HOM
查看及管理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)

#實例

[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

注意需要注釋掉/etc/profile文件里面的JAVA_HOM

[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(鏈接路徑【link】:/usr/bin/java  鏈接名【name】:java 應用程序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'.
Selection Command

• 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
  There are 2 programs which provide 'java'.
  Selection Command

  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: 1

  [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)