Use java's ArrayList.size() function to get the size of an ArrayList

Use Java's ArrayList.size() function to obtain the size of ArrayList

ArrayList is a commonly used dynamic array in Java, and its size can be dynamically increased or decreased according to demand. In programming, it is often necessary to obtain the size of an ArrayList for subsequent operations. Java provides the size() function of ArrayList to obtain its size.

The size() function of ArrayList returns the number of elements actually stored in the ArrayList, that is, the number of elements. For an empty ArrayList, its size is 0. Let's look at some examples to explain in detail the usage of ArrayList's size() function.

First, we need to import the ArrayList class in the java.util package. You can use the following code to import:

import java.util.ArrayList;

Then we can define an ArrayList object and add some elements, and then get its size through the size() function size. The following is a sample code:

import java.util.ArrayList;

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

        // 添加一些元素
        fruits.add("apple");
        fruits.add("banana");
        fruits.add("mango");

        // 获取ArrayList的大小
        int size = fruits.size();

        // 输出结果
        System.out.println("ArrayList的大小为：" + size);
    }
}

Run the above code, the output result is: "The size of ArrayList is: 3". This shows that there are 3 elements in the ArrayList object fruits.

In addition to obtaining the size of the ArrayList, the size() function can also be used to determine whether the ArrayList is empty. You can determine whether the ArrayList is empty by judging whether the return value of the size() function is 0. For example:

// 判断ArrayList是否为空
if (fruits.size() == 0) {
    System.out.println("ArrayList为空");
} else {
    System.out.println("ArrayList不为空");
}

In addition, the size() function can also be used for loop traversal. You can use a for loop combined with the size() function to traverse the elements in the ArrayList. For example:

// 遍历ArrayList中的元素
for (int i = 0; i < fruits.size(); i++) {
    String fruit = fruits.get(i);
    System.out.println("第" + (i + 1) + "个水果是：" + fruit);
}

Through the above example, we can see the usage of ArrayList's size() function and its related applications. It can not only be used to obtain the size of the ArrayList, but can also be used to determine whether the ArrayList is empty and perform loop traversal and other operations.

To summarize, using Java’s ArrayList.size() function can easily obtain the size of ArrayList, that is, the number of elements. By defining an ArrayList object, adding some elements, and then getting its size through the size() function. At the same time, the size() function can also be used to determine whether the ArrayList is empty and perform loop traversal and other operations. In actual programming, we can flexibly use the size() function to operate ArrayList as needed to achieve richer functions.

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