关闭表单然后重新打开表单后，Java netbeans ArrayList重置为0

import java.util.ArrayList;

public class Form {
    private ArrayList<Integer> arrayList;

    public Form() {
        arrayList = new ArrayList<>();
    }

    public void resetArrayList() {
        arrayList.clear();
    }

    public void addElement(int element) {
        arrayList.add(element);
    }

    public ArrayList<Integer> getArrayList() {
        return arrayList;
    }

    public static void main(String[] args) {
        Form form = new Form();
        form.addElement(1);
        form.addElement(2);
        form.addElement(3);

        System.out.println("ArrayList before reset: " + form.getArrayList());

        // Reset ArrayList
        form.resetArrayList();

        System.out.println("ArrayList after reset: " + form.getArrayList());
    }
}