3.5 Jmeter Beanshell PreProcessor生成随机数赋值变量

import java.util.Random; 

String random(int s_length) { 
      strings= "ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz"; 
      //int s_length = 10; 
      rstring ="";
      for (int i=0; i<s_length ; i++) { 
         Random randomGenerator = new Random(); 
         int randomInt = randomGenerator.nextInt(strings.length()); 
         rstring += strings.substring(randomInt,randomInt+1);
      } 
      return rstring ; 
} 

//log.info(random(10)); 
//log.info(random(20)); 

vars.put("random_10", random(10));     
vars.put("random_20", random(20));