Review

To get one (arbitrary) value from a set you can call Set.iterator().next(), but this throws if the set is empty.

Check that Set.isEmpty() is false.

• missing/condition/value_or_state

SetFirst.java

misuse(Set)

class SetFirst {
	public Object misuse(Set<Object> set) {
		return set.iterator().next();
	}

}

public class IsNotEmpty {
	void pattern(Set<Object> set) {
		if (!set.isEmpty()) {
			set.iterator().next();
		}
	}
}