If you are not familiar with how WebSphere integrates with Java, refer to Getting Started with Java on WebSphere.

The managesdk.bat (Windows) or managesdk.sh (Linux) command with the -listEnabledProfile option can be used to list the version of Java being used by the nodes and application servers in a profile. 

The -listEnabledProfileAll option can be used to list the version of Java being used by all profiles.

AVOID TROUBLE

If you are prompted for a username and password, refer to username password and the soap.client.props sas.client.props ipc.client.props files.

~]# ${WAS_INSTALL_ROOT}/bin/managesdk.sh -listEnabledProfile -profileName Profile01
CWSDK1006I: PROFILE_COMMAND_SDK = 1.7_32
CWSDK1008I: Node Node01 SDK name: 1.7_32
CWSDK1009I: Server Server01 SDK name: 1.8_32
CWSDK1009I: Server Server02 SDK name: 1.8_32

When starting your WebSphere network deployment manager (dmgr), node, or application server, the HPEL or SystemOut log should contain something like this, where the Java version matches the Java version being returned by the managesdk command.

Java version = 1.8.0_211, Java Runtime Version = 8.0.5.37 - pxa6480sr5fp37-20190618_01(SR5 FP37), Java Compiler = j9jit29, Java VM name = IBM J9 VM
Java Home = /opt/WebSphere/AppServer90/java/jre