How to use the ArrayList.clear() method in Java to clear elements in a list?

ArrayList in Java is a very commonly used data structure that allows us to dynamically store and manipulate data. In some cases, we may need to clear all elements in the list to refill or free up memory space. The ArrayList class provides a clear() method that can help us achieve this goal easily.

The clear() method is a member method of the ArrayList class, used to delete all elements in the list. This method is very simple, it does not receive any parameters and does not return any value. When we call the clear() method of the ArrayList object, it removes all elements from the list and resets the length of the list to 0.

The following is a sample code for clearing ArrayList:

import java.util.ArrayList;

public class ClearArrayListExample {
    public static void main(String[] args) {
        // 创建一个ArrayList对象并添加一些元素
        ArrayList<String> list = new ArrayList<>();
        list.add("元素1");
        list.add("元素2");
        list.add("元素3");

        System.out.println("清空前的列表内容：" + list);

        // 调用clear()方法清空列表
        list.clear();

        System.out.println("清空后的列表内容：" + list);
    }
}

Run the above code, the output result is as follows:

清空前的列表内容：[元素1, 元素2, 元素3]
清空后的列表内容：[]

As can be seen from the results, the clear() method will All elements of are removed and the list becomes an empty list.

It should be noted that the clear() method only deletes the elements in the list, but does not release the memory space occupied by the ArrayList object. The reference to the ArrayList object itself still exists, just the list is empty. If you want to completely free the memory, you can set the ArrayList object to null or recreate a new ArrayList object.

In short, we can easily clear the elements in the list by calling the clear() method of ArrayList to prepare for subsequent operations. This method is very simple and easy to use, and is a commonly used method when we deal with ArrayList.

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