How do I get the lastbuild parameters used in jenkins through groovy script?

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Groovy

Jenkins

I need to get the build parameters used in the last build of Jenkins job through Groovy script. I tired both instance.getItem and instance.getItemMap, but both are failing

What I have tried:

I tried below groovy script but getting an error on build.

import jenkins.model.Jenkins
def VAL1 = jenkins.model.Jenkins.instance.getItem('JOBNAME').lastBuild.getBuildVariables().get("PARAM")
def VAL2 = jenkins.model.Jenkins.instance.getItemMap()['JOBNAME'].lastBuild.getBuildVariables().get("PARAM")

ERROR: Build step failed with exception
java.lang.NullPointerException: Cannot get property 'lastBuild' on null object
	at org.codehaus.groovy.runtime.NullObject.getProperty(NullObject.java:60)
	at org.codehaus.groovy.runtime.InvokerHelper.getProperty(InvokerHelper.java:172)
	at org.codehaus.groovy.runtime.callsite.NullCallSite.getProperty(NullCallSite.java:47)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGetProperty(AbstractCallSite.java:296)
	at Script1.run(Script1.groovy:2)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:585)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:623)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:594)
	at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript.evaluate(SecureGroovyScript.java:170)
	at hudson.plugins.groovy.SystemGroovy.run(SystemGroovy.java:95)
	at hudson.plugins.groovy.SystemGroovy.perform(SystemGroovy.java:59)
	at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
	at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:779)
	at hudson.model.Build$BuildExecution.build(Build.java:205)
	at hudson.model.Build$BuildExecution.doRun(Build.java:162)
	at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:534)
	at hudson.model.Run.execute(Run.java:1720)
	at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
	at hudson.model.ResourceController.execute(ResourceController.java:98)
	at hudson.model.Executor.run(Executor.java:410)
Build step 'Execute system Groovy script' marked build as failure