Use java's ArrayList.addAll() function to add elements of one ArrayList to another ArrayList

Use Java's ArrayList.addAll() function to add elements of one ArrayList to another ArrayList

In Java, ArrayList is a very commonly used data structure that can dynamically store and manage a set of object. Sometimes we need to add elements of an ArrayList to another ArrayList. In this case, we can use the addAll() function of ArrayList to achieve this. Let's introduce the usage and sample code of this function in detail.

The addAll() function of ArrayList has the following syntax:

public boolean addAll(Collection<? extends E> c)

This function adds all elements in the specified collection (i.e. parameter c) to the ArrayList that calls the function. It returns a Boolean value indicating whether the call was successful.

The following sample code will demonstrate how to use the addAll() function of ArrayList to add elements of an ArrayList to another ArrayList:

import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        // 创建两个ArrayList
        ArrayList<String> list1 = new ArrayList<>();
        ArrayList<String> list2 = new ArrayList<>();

        // 给list1添加元素
        list1.add("Apple");
        list1.add("Banana");
        list1.add("Orange");

        // 给list2添加元素
        list2.add("Pineapple");
        list2.add("Strawberry");

        // 使用addAll()函数将list2的元素添加到list1中
        list1.addAll(list2);

        // 输出合并后的list1
        System.out.println("合并后的list1: " + list1);
    }
}

Run the above code, the output results are as follows:

合并后的list1: [Apple, Banana, Orange, Pineapple, Strawberry]

In the sample code, two ArrayLists are first created, namely list1 and list2. Then use the add() function to add the corresponding elements to list1 and list2. Next, use the addAll() function to add the elements of list2 to list1. Finally, print the merged list1 through the output statement.

To summarize, by using the addAll() function of Java's ArrayList, we can easily add elements of one ArrayList to another ArrayList. This is very useful when working with collection data. Hope this article is helpful to you!

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