Set Interface

Set.java

public interface Set<E> extends Collection<E>{
 int size();
 boolean isEmpty();
 boolean contains(Object o);
 Iterator<E> iterator();
 Object[] toArray();
 <T> T[] toArray(T[] a);
 boolean add(E e);
 boolean remove(Object o);
 boolean containsAll(Collection<?> c);
 boolean addAll(Collection<? extends E> c);
 boolean retainAll(Collection<?> c);
 boolean removeAll(Collection<?> c);
 void clear();
 boolean equals(Object o);
 int hashCode();
}

A Set is a collection, which can't contain duplicate elements. A Set contains exactly the same methods that Collection provides, but adds a restriction that duplicates are not allowed.

Two Sets are said to be equal if they contain same elements.

A Set extends the Collection interface, Where as HashSet, TreeSet and LinkedHashSet implements the Set interface.

A Set can contain a null element.

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