Collection - Interfaces in Java

In Java, the Collections Framework defines several core interfaces that provide a standardized way to work with collections of objects. These interfaces serve as the foundation for various types of collections such as lists, sets, and maps. Understanding these interfaces is crucial when working with collections in Java. Here are the key collection interfaces in Java:

1. Collection Interface:

• java.util.Collection

• Represents a group of objects.

• Root interface for all collection types.

• Common methods include add(), remove(), size(), isEmpty(), contains(), and iterator().

2. List Interface:

• java.util.List

• Represents an ordered collection that allows duplicate elements.

• Allows access to elements by their index.

• Common implementations include ArrayList, LinkedList, and Vector.

3. Set Interface:

• java.util.Set

• Represents a collection that does not allow duplicate elements.

• Does not provide access to elements by their index.

• Common implementations include HashSet, LinkedHashSet, and TreeSet.

4. SortedSet Interface:

• java.util.SortedSet

• Extends the Set interface and maintains elements in sorted order.

• Common implementation is TreeSet.

5. NavigableSet Interface:

• java.util.NavigableSet

• Extends the SortedSet interface and adds navigation methods.

• Allows forward and backward element navigation.

• Common implementation is TreeSet.

6. Queue Interface:

• java.util.Queue

• Represents a collection designed for holding elements before processing.

• Supports operations like add(), remove(), and element().

7. Deque Interface:

• java.util.Deque

• Extends the Queue interface to support both FIFO and LIFO operations.

• Allows elements to be added or removed from both ends.

• Common implementation is ArrayDeque.

8. Map Interface:

• java.util.Map

• Represents a collection of key-value pairs.

• Keys are unique, and each key maps to a single value.

• Common implementations include HashMap, LinkedHashMap, and TreeMap.

9. SortedMap Interface:

• java.util.SortedMap

• Extends the Map interface and maintains keys in sorted order.

• Common implementation is TreeMap.

10. NavigableMap Interface:

• java.util.NavigableMap

• Extends the SortedMap interface and adds navigation methods.

• Allows forward and backward key navigation.

• Common implementation is TreeMap.

These collection interfaces provide a consistent and unified way to work with different types of collections in Java. Implementing classes for these interfaces offer specific behaviors and characteristics, making it easier to choose the appropriate collection type for your application's needs.

For example, if you need a list that allows duplicate elements and maintains the order of insertion, you can use the List interface with an ArrayList implementation. If you require a set that does not allow duplicates and does not maintain any specific order, you can use the Set interface with a HashSet implementation. The choice of interface and implementation depends on your specific use case and requirements.