Collection interface

Collection interface

In this tutorial, we are going to discuss collection interface in java. It is a part of java.util package. It is one of the root interfaces of the Collection Hierarchy. Any class does not directly implement the Collection interface.

• If we want to represent a group of individual objects as a single entity, then we should go for the Collection interface.
• The Collection interface defines the most common general methods which can be applicable for any Collection object.
• The following is the list of methods present in the Collection interface.

boolean add(Object o);
boolean addAll(Collection c);
boolean remove(Object o);
boolean removeAll(Object o);
boolean retainAll(Collection c); // To remove all objects except those present in c.
void clear();
boolean contains(Object o);
boolean containsAll(Collection c);
boolean isEmpty();
int size();
Object[] toArray();
Iterator iterator();

  There is no concrete class which implements Collection interface directly.