Commonly used data structures in Java and their application scenarios

What are the common data structures in Java? Detailed explanation of Java data structure and application scenarios requires specific code examples

Data structure is a very important concept in computer science. It is a way of organizing and storing data. As a commonly used programming language, Java provides a rich data structure class library to facilitate developers to process various types of data. This article will introduce common data structures in Java and provide corresponding code examples.

1. Array (Array)
   Array is one of the most basic data structures, which can store a set of data of the same type. Arrays in Java have fixed size and elements can be accessed by index. Arrays are very efficient at storing and reading data, but they have a fixed size and cannot be dynamically expanded.

Code example:

int[] numbers = new int[5]; // 创建一个大小为5的整型数组
numbers[0] = 1; // 给数组的第一个元素赋值为1
int value = numbers[0]; // 读取数组的第一个元素

Application scenario: Suitable for storing fixed-size data, such as representing the grades of a group of students, weather forecast for seven days a week, etc.

2. Linked List
   A linked list is a dynamic data structure that consists of a series of nodes connected in a chain. Each node contains data and a reference to the next node. Java provides the LinkedList class to implement the linked list data structure.

Code example:

LinkedList<String> list = new LinkedList<>();
list.add("A"); // 向链表尾部添加数据
list.addFirst("B"); // 向链表头部添加数据
String first = list.getFirst(); // 获取链表头部的数据

Application scenario: Suitable for scenarios that require frequent insertion and deletion of elements, such as implementing data structures such as queues and stacks.

3. Stack (Stack)
   The stack is a last-in-first-out (LIFO) linear data structure that only allows elements to be inserted and deleted at the top of the stack. Java provides the Stack class to implement the stack data structure.

Code example:

Stack<Integer> stack = new Stack<>();
stack.push(1); // 压栈操作
int top = stack.peek(); // 获取栈顶元素，但不删除
int pop = stack.pop(); // 出栈操作

Application scenarios: Suitable for scenarios that need to meet the last-in-first-out characteristics, such as call stacks, expression evaluation, etc.

4. Queue (Queue)
   The queue is a first-in-first-out (FIFO) linear data structure that allows elements to be inserted at the end of the queue and elements to be deleted from the head of the queue. Java provides the Queue interface and its implementation classes to implement queue data structures, such as LinkedList, ArrayDeque, etc.

Code example:

Queue<Integer> queue = new LinkedList<>();
queue.offer(1); // 入队操作
int peek = queue.peek(); // 获取队首元素，但不删除
int poll = queue.poll(); // 出队操作

Application scenarios: Suitable for scenarios that need to meet the first-in-first-out characteristics, such as task scheduling, message queues, etc.

5. Hash table (HashMap)
   A hash table is a data structure that searches for a value (Value) based on a key (Key). It uses a hash function to map the key to the corresponding index position. . Java provides the HashMap class to implement the hash table data structure.

Code example:

HashMap<String, Integer> map = new HashMap<>();
map.put("A", 1); // 添加键值对
int value = map.get("A"); // 根据键获取值

Application scenario: Suitable for scenarios where elements need to be found quickly, such as dictionaries, caches, etc.

The above only introduces several common data structures in Java. In fact, Java also provides other data structures such as Heap, Tree, etc. Each data structure has its own characteristics. and applicable scenarios. In the actual programming process, developers should choose appropriate data structures according to specific needs to improve the performance and efficiency of the code.

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