Passing parameters of extendedChoice type to Jenkins Pipeline via jenkins-cli.jar

I have the following declarative pipeline. It defines checkbox multi-choice parameter:

pipeline {
    agent any 
    options {
        ansiColor('xterm')                    
    }
    parameters { 
        extendedChoice description: '', multiSelectDelimiter: ',', name: 'NAMES', quoteValue: false, saveJSONParameterToFile: false, type: 'PT_CHECKBOX', value:'a,b,c', visibleItemCount: 3
    } 
    stages {
      stage('Run on all') {

        steps { 
            script {
                  println params.NAMES 
            }
        }   
      }
    }

}

My goal is to call the pipeline via Jenkins CLI where passed values to NAMES parameter signifies selected checkboxes.

Running java -jar jenkins-cli.jar -s http://localhost:8080 -auth u:p -p NAMES='a' causes empty string to be printed by println params.NAMES

Expected a to be printed after calling the pipeline via Jenkins cli client.

The only way that worked is adding commas after a: java -jar jenkins-cli.jar -s http://localhost:8080 -auth u:p -p NAMES='a,,'

Is it the correct syntax to pass checkbox selections of extendedChoice type parameter?

Try with tokenize (,) since the options were saved like a string.
Save 'NAMES' into a new variable, then tokenize with a comma "," since it was configured the parameters with multiSelectDelimiter: ','
Finally, you can iterate the array with a for-loop and use the elements as desire.
def arr = userInput['NAMES'].tokenize(',')

arr.each { t ->
// t is the parameter option
sh("echo ${t}")
}


StackExchange DevOps Q#11797, answer score: 1