【Data Structures】 1. Collection，

【Data Structures】 1. Collection，

Collections in Java that are called the Java Collections Framework are a set of interfaces and classes that are available for you to use in the java.util. package

Java Collections Framework:

Interface	Implementation
List	ArrayList, LinkedList
Set	HashSet, TreeSet
Map	HashMap, TreeMap

Set extends Collection but forbids duplicates

List extends Collection also and allows duplicates and introduces positional indexing

Map extends neither Set nor List. Map is a collection of pair (key, value). Map cannot contain duplicate keys

General-Purpose Data Structure

1. Arrays

The amount of data is reasonably small

The amount of data is predictable in advance

2. Linked Lists

The amount of data is comparatively small

The amount of data cannot be predicted in advance

When data will frequently be inserted and deleted

3. Binary Search Trees

Generally, a binary search tree is the first structure to consider when arrays and linked lists prove too slow

It provides fast insertion, searching, and deletion

When you are sure that the input data will arrive in random order (Ordered data as an input can reduce its performance, no better than a linked list)

4. Hash Tables

Generally, the fastest, expecially for search, insertion, and deletion

Not sensitive to the order in which data is inserted

Requires additional memory

Performance is affected by initial capacity and load factor

Special-Purpose Data Structure

1. Stack

Used when a program needs to access only the last data item inserted (LIFO)

2. Queue

Used when a program needs to access only the first item inserted (FIFO)

3. Priority Queue

Used when the only access desired to the data item with the highest priority

Can be implemented using an array, a linked list or a heap. When speed is important, a heap is a better choice

Common operations:

Addition (Insertion), Removal (Deletion), Sorting, Searching, Iteration (Traversal), Copying (Cloning)