How to change the JDK for a Jenkins job?

I have imported the jenkins jobs from existing jenkins server from another machine. But the problem is, it has the JDK referenced as per the old machines and I want to change it to use the JDK configured in my new jenkins. But I am unable to find any way of doing this. So, please if you have come across this situation and found a way then please help me too.

Thanks.

There is a JDK dropdown in "job name" -> Configure in Jenkins web ui. It will list all JDKs available in Jenkins configuration.

For existing jobs you're editing, the JDK drop-down choice may not be available if you've just added a single JDK config in the 'Configure System' Jenkins settings.

However, it is available for new jobs.

Surprisingly, if you add a second JDK config, it becomes available in an existing job too.

This looks to me like a bug (tested in Jenkins ver. 1.629).

See a similar issue raised here: JDK selection is hidden even when a JDK is configured