Use java's ArrayList.clear() function to clear the elements in the ArrayList

Use Java's ArrayList.clear() function to clear the elements in the ArrayList

In Java programming, ArrayList is a very commonly used data structure that can dynamically store and access elements. However, in some cases, we may need to clear all elements in the ArrayList in order to reuse or free the memory. At this time, you can use the clear() function of ArrayList to achieve it.

The ArrayList.clear() function is a method in the ArrayList class, used to clear all elements in the ArrayList. Its function is to set the size of the ArrayList to 0, thus deleting all elements. The cleared ArrayList still exists and new elements can continue to be added.

The following code example demonstrates how to use the ArrayList.clear() function to clear the elements in the ArrayList:

import java.util.ArrayList;

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

        // 添加元素到ArrayList
        list.add("元素1");
        list.add("元素2");
        list.add("元素3");
        list.add("元素4");

        // 打印ArrayList的初始内容
        System.out.println("ArrayList的初始内容为：" + list);

        // 使用clear()函数清空ArrayList中的元素
        list.clear();

        // 打印清空后的ArrayList内容
        System.out.println("清空后的ArrayList内容为：" + list);
    }
}

Run the above code, the output is as follows:

ArrayList的初始内容为：[元素1, 元素2, 元素3, 元素4]
清空后的ArrayList内容为：[]

You can see After clearing the ArrayList, the size of the ArrayList is set to 0, that is, there are no elements. The clear() function deletes all elements in the ArrayList at once to achieve the purpose of clearing.

It should be noted that the ArrayList.clear() function will only delete the elements in the ArrayList and will not release the memory occupied by the ArrayList object itself. If you need to release the memory occupied by the ArrayList object, you can do so by assigning the value of the object to null.

list = null;

To summarize, using Java’s ArrayList.clear() function can easily clear the elements in ArrayList. This method is very simple and efficient, and is suitable for scenarios where ArrayList objects need to be reused or released.

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