I am unable to use string functions in my groovy file.

I have added required headers in script security xml. Please help me to resolve
In finally FAILURE[Pipeline] End of Pipeline[Bitbucket] Notifying commit build result
[Bitbucket] Build result notified
hudson.remoting.ProxyException: groovy.lang.MissingMethodException: No signature of method: java.util.ArrayList.tokenize() is applicable for argument types: (java.lang.String) values: [,]
Possible solutions: toUnique(), toUnique(), takeWhile(groovy.lang.Closure), takeWhile(groovy.lang.Closure), toUnique(groovy.lang.Closure), toUnique(java.util.Comparator)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:121)
at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:153)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:157)
at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.methodCall(SandboxInvoker.java:16)