title: replace null to empty string in Java
body: <p>I have below string output :</p>
  
  <pre><code>["Kolkata","data can be, null",null,"05/31/2020",null]
  </code></pre>
  
  <p>but I want to have the output like below format in Java</p>
  
  <pre><code>["Kolkata","data can be, null","","05/31/2020",""]
  </code></pre>
  
  <p>please help me .</p>
  
  <p>I am converting object to json data . Please see the below codes             </p>
  
  <pre><code>List&lt;String&gt; test = new ArrayList&lt;&gt;();
  List&lt;Object[]&gt; data =query.list();          
  for (int i = 0; i &lt; data.size(); i++) {
      Object[] row = (Object[]) data.get(i);
  
      String  jsonString = gson.toJson(row);
      test.add(jsonString);
  } 
  </code></pre>
  
  <p>I want to apply this on jsonString variable using java 7 as not using java 8</p>