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<h4>NULL_VALUE</h4>
<pre>public static final&nbsp;<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</a> NULL_VALUE</pre>
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 Because <code>null</code> values are not allowed as the source for subclasses of <code>Even