Summary of List collection in Java

Introduction to List collection in Java

In Java programming, List is one of the commonly used collection classes. It provides an ordered collection that can store a sequence of elements and allows elements to be repeated. The List interface inherits from the Collection interface and provides some other methods to operate elements in the collection. The following will introduce in detail the characteristics, common methods and code examples of List collections.

1. Characteristics of List collection

• List collection is ordered, and each element is accessed through an index. This index starts from 0 and increases sequentially. An element can be added, removed, or accessed based on its index.
• List collection allows duplicate elements. The same element can be added to the collection multiple times.
• List collection can be dynamically resized. Elements in the collection can be added or subtracted at any time as needed.

2. Common methods

• add(Object element): Add an element to the List collection.
• remove(int index): Remove an element from the List collection based on the index.
• get(int index): Get an element from the List collection according to the index.
• size(): Returns the number of elements in the List collection.
• contains(Object element): Determine whether the List collection contains the specified element.
• indexOf(Object element): Returns the index of the specified element in the List collection.
• addAll(Collection c): Add all elements in a Collection to the List collection.
• clear(): Clear all elements in the List collection.

The following are some code examples of List collections:

import java.util.ArrayList;
import java.util.List;

public class ListExample {
    public static void main(String[] args) {
        // 创建一个List集合
        List<String> list = new ArrayList<>();

        // 向List集合中添加元素
        list.add("apple");
        list.add("banana");
        list.add("orange");

        // 根据索引获取元素
        System.out.println("第二个元素是: " + list.get(1));

        // 获取List集合的大小
        System.out.println("List集合的大小是: " + list.size());

        // 判断List集合是否包含某个元素
        System.out.println("List集合是否包含apple: " + list.contains("apple"));

        // 删除List集合中的元素
        list.remove(0);
        System.out.println("删除第一个元素后的List集合: " + list);

        // 清空List集合
        list.clear();
        System.out.println("清空List集合后的大小: " + list.size());
    }
}

The output result is:

第二个元素是: banana
List集合的大小是: 3
List集合是否包含apple: true
删除第一个元素后的List集合: [banana, orange]
清空List集合后的大小: 0

Through the above code examples, you can see the basic usage of List collections, Including operations such as adding, deleting, obtaining elements, and determining the size of the List collection.

Summary: List collection is one of the commonly used collection classes in Java. It provides an ordered collection that allows duplication of elements. By using the List collection, you can operate on a series of elements more conveniently. In actual development, we often use List collections to store and manage data. I hope that through the introduction of this article, readers will have a deeper understanding of the List collection.

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