This also allows duplicate data to be present in it. Otherwise, returns false. Queue: As the name suggests, a queue interface maintains the FIFO(First In First Out) order similar to a real-world queue line. Returns the number of elements in this collection. Removes all elements from the invoking collection except those in c. Returns true if the collection changed (i.e., elements were removed). boolean addAll ( Collection C ) Add all elements of collection C to the invoking collection. There are various classes like PriorityQueue, Deque, ArrayDeque, etc. Reference: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Collection.html. Returns true if this Collection contains no elements. Because all collections implement Collection, familiarity with its methods is necessary for a clear understanding of the framework. It is one of the root interfaces of the Collection Hierarchy. close, link It is a part of java.util package. Set: A set is an unordered collection of objects in which duplicate values cannot be stored. Please use ide.geeksforgeeks.org, generate link and share the link here. This interface extends the queue interface. boolean add ( E obj ) Used to add objects to a collection. Returns true if obj was added to the collection. The add(E e) and addAll(Collection c) methods provided by Collection can be used to add elements. The Collection interface is the root interface of the Java collections framework. Returns false if obj is already a member of the collection, or if the collection does not allow duplicates. Returns true if this Collection contains the specified... toArray. Returns true if obj is an element of the invoking collection. A Collection represents a group of objects known as its elements. Since this class implements the deque, we can instantiate a deque object with this class. Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below. edit It is one of the root interfaces of the Collection Hierarchy. Removes one instance of obj from the invoking collection. This interface is dedicated to the … 2. boolean addAll (Collection c) Adds all the elements of c to the invoking collection. Since all the subclasses implement the set, we can instantiate a set object with any of these classes. For example. Since all these subclasses implement the queue, we can instantiate a queue object with any of these classes. Here, E is the type of elements stored in the collection. Returns true if this collection contains no elements. The class which implements this interface is TreeSet. See your article appearing on the GeeksforGeeks main page and help other Geeks. How to remove an element from ArrayList in Java? Creates a Spliterator over the elements in this collection. Returns the number of elements in this Collection. Removes all elements from the invoking collection. By using our site, you To iterate over the elements of Collection we can use iterator() method. List Interface: This is a child interface of the collection interface. For Example, the HashSet class implements the Set interface which is a subinterface of the Collection interface. Retains only the elements in this collection that are contained in the specified collection (optional operation). These methods are summarized in the following table. Otherwise, returns false. The Collection interface is the foundation upon which the collections framework is built. Returns false if obj is already a member of the collection, or if the collection does not allow duplicates. Following is an example to explain few methods from various class implementations of the above collection methods −. Returns true if the invoking collection is empty. It is a part of java.util package. The List interface is found in the java.util package and inherits the Collection interface. Adds all the elements in the specified collection to this collection (optional operation). Otherwise, returns false. Returns true if the invoking collection contains all elements of c. Otherwise, returns false. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. For example. Returns true if the element was removed. 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Several of these methods can throw an UnsupportedOperationException. This interface is dedicated to the data of the list type in which we can store all the ordered collection of the objects. Experience. This set interface is implemented by various classes like HashSet, TreeSet, LinkedHashSet, etc.