A key is an object that you use to access the value later, it is associated with a single value.The map interface in Java is a part of the interface.Map interface contains only unique keys and does not allow any duplicate keys.Each entry in the map store the data in a key and its corresponding value.The maps interface in java is a collection that links a key with value pairs. It behaves a little bit differently from the other collection types. Java's map interface has often been misunderstood as a subtype of the Collections interface. It is present in java.util package and store the data in key, value pairs where a key is an object that you use to later access the value. Some of the classes provide full implementations that can be used as-is and others are abstract class, providing skeletal implementations that are used as starting points for creating concrete collections.The map interface in java of the Java collections framework maps unique keys to the values. Java provides a set of standard collection classes that implement Collection interfaces. This legacy interface has been superceded by Iterator. This is legacy interface defines the methods by which you can enumerate (obtain one at a time) the elements in a collection of objects. This extends Map so that the keys are maintained in an ascending order. This describes an element (a key/value pair) in a map. This extends Collection to handle sets, which must contain unique elements. This extends Collection and an instance of List stores an ordered collection of elements. This enables you to work with groups of objects it is at the top of the collections hierarchy. This section provides an overview of each interface − The collections framework defines several interfaces. Although maps are not collections in the proper use of the term, but they are fully integrated with collections. In addition to collections, the framework defines several map interfaces and classes. The algorithms are said to be polymorphic: that is, the same method can be used on many different implementations of the appropriate collection interface. In essence, they are reusable data structures.Īlgorithms − These are the methods that perform useful computations, such as searching and sorting, on objects that implement collection interfaces. Implementations, i.e., Classes − These are the concrete implementations of the collection interfaces. In object-oriented languages, interfaces generally form a hierarchy. Interfaces allow collections to be manipulated independently of the details of their representation. Interfaces − These are abstract data types that represent collections. All collections frameworks contain the following − Several standard implementations such as LinkedList, HashSet, and TreeSet, of these interfaces are provided that you may use as-is and you may also implement your own collection, if you choose.Ī collections framework is a unified architecture for representing and manipulating collections. Towards this end, the entire collections framework is designed around a set of standard interfaces. The framework had to extend and/or adapt a collection easily. The framework had to allow different types of collections to work in a similar manner and with a high degree of interoperability. The implementations for the fundamental collections (dynamic arrays, linked lists, trees, and hashtables) were to be highly efficient. The framework had to be high-performance. The collections framework was designed to meet several goals, such as − Thus, the way that you used Vector was different from the way that you used Properties. Although these classes were quite useful, they lacked a central, unifying theme. Prior to Java 2, Java provided ad hoc classes such as Dictionary, Vector, Stack, and Properties to store and manipulate groups of objects.
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