 Instead, consider defining a sentinel object with the intended semantics
  or use library types like <code>Optional</code> to denote the absence of a value.</p>
<p><b>Example:</b></p>
<pre><code>
  Integer convert(String s) {
    Integer value;
    try {
      value = Integer.parseInt(s);
    } catch (NumberFormatException e) {
      // Warning: null is used to denote an 'invalid value'
      value = null;
    }
    return value;
  }
</code></pre>
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<p>
Use the <b>Ignore assignments to f