title: why does print vars.put ,the result is null?
body: <pre><code>String pass = "123456789";
  vars.put("token01",pass);
  System.out.println(pass);
  System.out.println(token01);
  </code></pre>
  
  <p>the result of System.out.println(pass) is right ,it is 123456789,
  but the result of token01 is null, I can not understand .</p>