import groovy.json.JsonSlurper
import groovy.json.JsonOutput 
class Example {
 
   static void main(String[] args) {
        def jsonSlurper = new JsonSlurper()
        def obj = jsonSlurper.parseText '''{"-1":     {"description": "test1"},"222":     {"description": "test2"},"223":     {"description": "test3"},"224":     {"description": "test4"},"recordsCount": 4}'''
    	//println(obj.keySet()); //[-1, 222, 223, 224, recordsCount]
    	Set<String> keySet=obj.keySet();
    	List<String> keys =  [];
    	for(String key:keySet){
    	    if(key.isNumber())
    	        keys.add(key);
    	}
    	//println(keys); //[-1, 222, 223, 224]
    	def output = JsonOutput.toJson(keys);
        //println(output); //["-1","222","223","224"]
        println output.toString()
   } 
}

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