/7/docs/api/java/util/Collections.html?is-external=true#unmodifiableMap-java.util.Map-" title="class or interface in java.util"><code>Collections.unmodifiableMap(java.util.Map&lt;? extends K, ? extends V&gt;)</code></a>, this method must return
 <code>true</code>. Unfortunately, there is no Collections API method to detect this. However, an implementation can
 create a prototype unmodifiable <code>Map</code> and query its runtime type to see if it matches the runtime type of
 the base object as a workaround