ava.lang.Object)" title="class or interface in java.util" class="external-link">contains</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/HashSet.html#isEmpty()" title="class or interface in java.util" class="external-link">isEmpty</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/HashSet.html#iterator()" title="class or interface in java.util" class="external-link">iterator</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/ap