title: "Result of method is ignored"- what does this imply?
body: <p>For some methods I get the warning. This is what it says when expanded. 
  The following code (<code>mkDirs()</code>) gives the warning</p>
  
  <pre><code>if (!myDir.exists()) {
       myDir.mkdirs();
  }
  </code></pre>
  
  <blockquote>
    <p>Reports any calls to specific methods where the result of that call is ignored. Both methods specified in the inspection's settings and methods annotated with org.jetbrains.annotations.Contract(pure=true) are checked. For many methods, ignoring the result is perfectly legitimate, but for some methods it is almost certainly an error. Examples of methods where ignoring the result of a call is likely to be an error include java.io.inputStream.read(), which returns the number of bytes actually read, any method on java.lang.String or java.math.BigInteger, as all of those methods are side-effect free and thus pointless if ignored.</p>
  </blockquote>
  
  <p>What does it mean? How to to avoid it? How should it be addressed?</p>