title: String.format() adding 2 blank spaces when arguments are empty strings
body: <p>I have this simple method that goes:</p>
  
  <pre><code>private String toJsonFormat(String name, Object value, boolean first) {
      value = value == null ? "" : value; 
      return String.format((first ? "" : ",") + "\"%1s\":\"%2s\"", name, value);
  }
  </code></pre>
  
  <p>When my <em>value</em> argument is <code>null</code>, 2 blank spaces are added after the colon, instead of an empty string.</p>
  
  <p>An example return value when <code>null</code> is passed:</p>
  
  <pre><code>"housenumber":"  "
  </code></pre>
  
  <p>How come?</p>