Introduction to collection Implementations

The Collections Framework provides a well-designed set of interfaces and classes used for storing and manipulating groups of data into a single unit. The collections framework is a unified architecture which is used to represent and manipulate collections. The framework allows the collections to get manipulated independently as well as reduces programming effort for increasing performance. 
It includes implementations of interfaces, and algorithms included in it to manipulate them. Basically it is a unified architecture that consists the following collections:  

Implementations are the reusable data objects used to store collections, which implement the collection interfaces.  Implementations are also responsible for documenting the operations which they support. All of the general-purpose implementations of the Java platform support all of the optional operations.

• General-purpose implementations: These are the most commonly used implementations, designed for performing all optional operations contained within the defined interfaces. They are summarized in the table below.
  

• The Java Collections Framework provides several general-purpose implementations of the Set, List , and Map interfaces. Each of the general-purpose implementations provides all optional operations contained in its interface. All permit null elements, keys, and values.

• Special-purpose implementations: These are designed to use in special situations and display nonstandard performance characteristics, usage restrictions, or behavior.
  
• Concurrent implementations: These are designed to support high concurrency. These implementations are part of the java.util.concurrent package.
  
• Wrapper implementations: These are used in combination with other types of implementations.
  
• Convenience implementations: These are mini-implementations, typically made via static factory methods, that provide convenient, efficient alternatives to general-purpose implementations for special collections.
  
• Abstract implementations: These are implementations that facilitate the construction of custom implementations.

The following description describes the categories in which the Collection Framework interfaces are implemented.

The Set implementations are grouped into general-purpose and special-purpose implementations. List implementations are grouped into general-purpose and special-purpose implementations. Map implementations are grouped into general-purpose, special-purpose, and concurrent implementations. The Queue implementations are grouped into general-purpose and concurrent implementations.