This is one of the most confusing java interview question asked many a times to java freshers. Most of time, this question has been asked to java freshers to check their basic knowledge about the Java Collection Framework. This question seems confusing because both “Collection” and “Collections” look similar. Both are part of java collection framework, but both serve different purpose. Collection is a top level interface of java collection framework where as Collections is an utility class. In this article, we will discuss the differences between Collection and Collections in java.
Collection is a root level interface of the Java Collection Framework. Most of the classes in Java Collection Framework inherit from this interface. List, Set and Queue are main sub interfaces of this interface. JDK doesn’t provide any direct implementations of this interface. But, JDK provides direct implementations of it’s sub interfaces. ArrayList, Vector, HashSet, LinkedHashSet, PriorityQueue are some indirect implementations of Collection interface. Map interface, which is also a part of java collection framework, doesn’t inherit from Collection interface. Collection interface is a member of java.util package.
Collections is an utility class in java.util package. It consists of only static methods which are used to operate on objects of type Collection. For example, it has the method to find the maximum element in a collection, it has the method to sort the collection, it has the method to search for a particular element in a collection.
Main differences between Collection and Collections are as follows:
I. Collection is an interface in Java. But Collections is a class in Java.
II. Collection is a base interface. Collections is a utility class in Java.
III. Collection defines methods that are used for data structures that contain the objects. Collections defines the methods that are used for operations like access, find etc. on a Collection.
Collection is a root level interface of the Java Collection Framework. Most of the classes in Java Collection Framework inherit from this interface. List, Set and Queue are main sub interfaces of this interface. JDK doesn’t provide any direct implementations of this interface. But, JDK provides direct implementations of it’s sub interfaces. ArrayList, Vector, HashSet, LinkedHashSet, PriorityQueue are some indirect implementations of Collection interface. Map interface, which is also a part of java collection framework, doesn’t inherit from Collection interface. Collection interface is a member of java.util package.
Collections is an utility class in java.util package. It consists of only static methods which are used to operate on objects of type Collection. For example, it has the method to find the maximum element in a collection, it has the method to sort the collection, it has the method to search for a particular element in a collection.
Main differences between Collection and Collections are as follows:
I. Collection is an interface in Java. But Collections is a class in Java.
II. Collection is a base interface. Collections is a utility class in Java.
III. Collection defines methods that are used for data structures that contain the objects. Collections defines the methods that are used for operations like access, find etc. on a Collection.
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