如果在Ubuntu上安装了多个Java版本，如何检查Oracle Java版本

Question

I have both OpenJDK and Oracle Java installed on my Ubuntu. If the activated java is OpenJDK, is there a way to check the version of Oracle java in bash shell?

Answer 1

update-java-alternatives -l will list all the java versions installed via the alternatives system.

For instance on one of my systems it will display the version and the path:

java-1.6.0-openjdk-amd64 1061 /usr/lib/jvm/java-1.6.0-openjdk-amd64
java-7-oracle 1069 /usr/lib/jvm/java-7-oracle

If you want the oracle one then I guess you could do:

update-java-alternatives -l | grep oracle | awk '{ print $1 }'

This would alternatively find all oracle versions and issue the -version command against each one in the list:

update-java-alternatives -l | grep oracle | awk '{system($3"/bin/java -version")}'

Output may look something like this:

java version "1.7.0_67"
Java(TM) SE Runtime Environment (build 1.7.0_67-b01)
Java HotSpot(TM) 64-Bit Server VM (build 24.65-b04, mixed mode)

One step further would be to parse out the java version from the -version command and simply display it:

(update-java-alternatives -l | grep oracle | awk '{system(""$3"/bin/java -version 2>&1 | grep \"java version\"")}') | awk -F\" '{print $2}'

The 2>&1 is needed because Java will display version to standard error. The output would simply look like this (and could be easily assigned to a bash variable if you needed it that way):

1.7.0_67

If you had multiple oracle instances this would display the version for each one. If you wanted to find all the versions for every Java you could simply remove the | grep oracle | grep oracle

Answer 2

If you are using the openjdk java, then the oracle Java in your PC is just a folder. There is no command to check the version of that if you are not using it.

If you once used oracle java then it must be in your java alternatives and you can find the folder (usually with version in name) with:

update-alternatives --config java

If it says something like /usr/lib/jvm/jdk1.8.0_05/bin/java , then you have 1.8 in your pc.

If you haven't used oracle java anytime you simply have to check what you have downloaded.

If you want to simply see the version you are using:

java -version

Hope it helps

Answer 3

yes, you need to know the install path of the oracle one. then /path/to/there/bin/java -version . Assume that the openjdk one is your default java.

Answer 4

Go to the installation folder of the oracle Java, and then open the bin folder. Now open a terminal "here" and type java -version

alternativelly,

paste the entire path to that bin folder in the command line followed by java -version ie /path/to/bin/java -version

Answer 5

you should follow bellow two commands

1. sudo update-alternatives --config java

In their show the all already installed Java versions like below

2.gedit ~/.bashrc

`export JAVA_HOME=/path/to/jdk/folder

usually /usr/java/jdk or /usr/lib/java/jdk

export PATH=$PATH:$JAVA_HOME/bin`

add to bash