How to get java path in CentOS?

try this if java command works

readlink -f $(which java)

Here are the solution

# cd /opt/jdk1.7.0_79/
# alternatives --install /usr/bin/java java /opt/jdk1.7.0_79/bin/java 2
# alternatives --config java
# alternatives --install /usr/bin/jar jar /opt/jdk1.7.0_79/bin/jar 2
# alternatives --install /usr/bin/javac javac /opt/jdk1.7.0_79/bin/javac 2
# alternatives --set jar /opt/jdk1.7.0_79/bin/jar
# alternatives --set javac /opt/jdk1.7.0_79/bin/javac 
# java -version

java version "1.7.0_79"
Java(TM) SE Runtime Environment (build 1.7.0_79-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

# export JAVA_HOME=/opt/jdk1.7.0_79
# export PATH=$PATH:/opt/jdk1.7.0_79/bin

Thanks to tecadmin

They usually reside in /usr/lib/jvm. You can list them via ll /usr/lib/jvm. The value you need to enter in the field JAVA_HOME in jenkins is /usr/lib/jvm/java-1.8.0-openjdk.

Update

when I look at '/usr/lib/jvm' I get ...

What you see there is a list of symbolic links pointing to a similar target located in /etc/alternatives. In the end they all point to the same target. The difference is only the name which allows you to choose how explicit your choice if the target version shall be.

(Because java-1.8.0-openjdk is missing: Maybe you also need to install the package java-1.8.0-openjdk-devel.)