title: Is a Guava Table thread safe when its backing maps are thread safe?
body: <p>Will Guava's <a href="https://google.github.io/guava/releases/22.0/api/docs/com/google/common/collect/Tables.html#newCustomTable-java.util.Map-com.google.common.base.Supplier-" rel="nofollow noreferrer">Tables.newCustomTable(Map, Supplier)</a> method return thread safe tables when supplied with thread safe maps?  For example:</p>
  
  <pre><code>public static &lt;R, C, V&gt; Table&lt;R, C, V&gt; newConcurrentTable() {
    return Tables.newCustomTable(
        new ConcurrentHashMap&lt;R, Map&lt;C, V&gt;&gt;(),
        new Supplier&lt;Map&lt;C, V&gt;&gt;() {
          public Map&lt;C, V&gt; get() {
            return new ConcurrentHashMap&lt;C, V&gt;();
          }
        });
  }
  </code></pre>
  
  <p>Does that code actually return concurrent tables?</p>