Java Collection Framework Practical Guide: Teach you step by step how to use the framework and solve practical problems

Java Collection Framework Practical Guide provides practical skills guidance for the majority of Java developers. PHP editor Banana has carefully compiled this guide to help readers master the usage skills of the Java collection framework and solve practical programming problems through step-by-step teaching methods. This guide comprehensively introduces various data structures and operation methods of the Java collection framework, allowing readers to apply it more flexibly in project development and improve code efficiency and quality.

List is an ordered collection in Javacollectionframework that allows elements to be repeated and elements can be accessed through index. Common implementation classes of List include ArrayList, LinkedList and Vector.

The following demonstrates how to use ArrayList to store a set of integers:

import java.util.ArrayList;

public class ArrayListDemo {

public static void main(String[] args) {
// 创建一个ArrayList对象
ArrayList<Integer> numbers = new ArrayList<>();

// 向ArrayList中添加元素
numbers.add(1);
numbers.add(3);
numbers.add(5);
numbers.add(7);

// 获取ArrayList的长度
int size = numbers.size();

// 获取ArrayList的第一个元素
int firstElement = numbers.get(0);

// 修改ArrayList的最后一个元素
numbers.set(size - 1, 9);

// 从ArrayList中删除一个元素
numbers.remove(2);

// 遍历ArrayList中的元素
for (int number : numbers) {
System.out.println(number);
}
}
}

Output result:

1
3
5
9

2. Set

Set is an unordered collection in the Java collection framework. Duplication of elements is not allowed, and elements cannot be accessed through indexes. Common implementation classes of Set include HashSet, TreeSet and LinkedHashSet.

The following demonstrates how to use HashSet to store a set of strings:

import java.util.HashSet;

public class HashSetDemo {

public static void main(String[] args) {
// 创建一个HashSet对象
HashSet<String> names = new HashSet<>();

// 向HashSet中添加元素
names.add("John");
names.add("Mary");
names.add("Bob");
names.add("Alice");

// 获取HashSet的长度
int size = names.size();

// 检查HashSet中是否存在某个元素
boolean exists = names.contains("John");

// 从HashSet中删除一个元素
names.remove("Bob");

// 遍历HashSet中的元素
for (String name : names) {
System.out.println(name);
}
}
}

Output result:

John
Mary
Alice

3. Map

Map is a collection of key-value pairs in the Java collection framework, where each key uniquely identifies a value. Commonly used implementation classes of Map include HashMap, TreeMap and LinkedHashMap.

The following demonstrates how to use HashMap to store a set of key-value pairs:

import java.util.HashMap;

public class HashMapDemo {

public static void main(String[] args) {
// 创建一个HashMap对象
HashMap<String, Integer> ages = new HashMap<>();

// 向HashMap中添加键值对
ages.put("John", 25);
ages.put("Mary", 30);
ages.put("Bob", 35);
ages.put("Alice", 40);

// 获取HashMap的长度
int size = ages.size();

// 获取HashMap中某个键对应的值
int age = ages.get("John");

// 检查HashMap中是否存在某个键
boolean exists = ages.containsKey("Bob");

// 从HashMap中删除一个键值对

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