Shulou(Shulou.com)06/02 Report--

Java is used to execute java programs (java runtime environment)

Javac is used in java program compilation (java program development environment)

Step 2: alternatives install JDK

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

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

Step 2: view the available version information

# alternatives-display java

# alternatives-display javac

Step 3: switch the java version

# alternatives-config java

# alternatives-config javac

Delete the jdk version (optional, use-- remove when you need to delete)

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

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

Step 4: modify the jdk runtime environment of the current user

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

Echo export PATH=$PATH:$JAVA_HOME/bin > > ~ / .bash_profile # source ~ / .bash_profile

Note that you need to comment out the JAVA_HOM in the / etc/profile file

View and manage 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)

# instance [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

Note that you need to comment out the JAVA_HOM in the / etc/profile file

[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

Step 1: alternatives install JDK1.7 (link path [link]: / usr/bin/java link name [name]: java application JAVA actual path [path]: / home/cqs/data/jdk/jdk1.7.0_80/bin/java priority [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 "1.7.080"

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 install 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 "1.7.080"

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

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

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