Set Interface in JAVA

A Set is a Collection that cannot contain duplicate elements. The set interface extends the Collection interface and, by definition, forbids duplicates within the collection.The Set interface contains only methods inherited from Collection and adds the restriction that duplicate elements are prohibited.

Following is the Set interface:

public interface Set<E> extends Collection<E> {
    // Basic operations
    int size();
    boolean isEmpty();
    boolean contains(Object element);
    // optional
    boolean add(E element);
    // optional
    boolean remove(Object element);
    Iterator<E> iterator();

    // Bulk operations
    boolean containsAll(Collection<?> c);
    // optional
    boolean addAll(Collection<? extends E> c);
    // optional
    boolean removeAll(Collection<?> c);
    // optional
    boolean retainAll(Collection<?> c);
    // optional
    void clear();

    // Array Operations
    Object[] toArray();
    <T> T[] toArray(T[] a);
}

Following table specifies the methods of Set interface:

Example:

package com.sample.javase.testing;

import java.util.Iterator;

import java.util.Set;

import java.util.TreeSet;

public class SetInterfaceExample {

/**

* @param args

*/

public static void main(String[] args) {

Set<Integer> set1 = new TreeSet<Integer>();

set1.add(new Integer(5));

set1.add(new Integer(6));

set1.add(new Integer(7));

System.out.println(set1);

for (Iterator<Integer> iterator = set1.iterator(); iterator.hasNext();) {

Integer integer = (Integer) iterator.next();

System.out.println("using iterator"+ integer);

}

}

}