'output repeats when I reload the page in JSP in Intellij idea

In the following code, I have a JSP file and a TodoList class. In the last line of JSP, the showList (out) method is called, which prints the Todo list. My problem is that every time I reload the page, the showList (out) method Is called, and the list is reprinted, but the interesting thing is that TODO LIST: <br> which was in the body of the method is not reprinted! Even previous out.prints() are not reprinted. Why is that?

servlet container: Tomcat 10.0

update: I changed the TODO LIST: <br> style because the <br> was considered as line breaker by the text editor.

jsp file:

<%@ page import="java.time.LocalDate" %>
<%@ page import="java.util.HashMap" %>
<%@ page import="java.util.Map" %>
<%@ page import="java.util.Iterator" %>
<%@ page import="com.isoft.TodoList" %>

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Hello Java Page</title>
</head>


<body>
<h3>Welcome Back! : <%=LocalDate.now()%>
</h3>

<p id="par"></p>
<%
    HashMap<Integer, String> students = new HashMap<>();
    students.put(391, "Ali");
    students.put(923, "Mohammad");
    students.put(123, "Ahmad");
    students.put(988, "Hossein");
    students.put(906, "Hamed");

    Iterator<Map.Entry<Integer, String>> iterator = students.entrySet().iterator();
    Map.Entry<Integer, String> student;

    out.print("Students with id > 500 :<br>");
    while (iterator.hasNext())
        if ((student = iterator.next()).getKey() > 500)
            out.print(student.getValue() + "<br>");
    out.print("<hr>");

    TodoList todoList = TodoList.getInstance();
    todoList.addItem("dentist", LocalDate.of(2022, 12, 23), "I should go to the dentist");
    todoList.addItem("park", LocalDate.of(2022, 10, 1), "I should go to the Park");
    
    todoList.showList(out);
</body>
</html>

TodoList class:

package com.isoft;

import jakarta.servlet.jsp.JspWriter;

import java.io.IOException;
import java.time.LocalDate;
import java.util.ArrayList;
import java.util.Optional;

public class TodoList {
    private static ArrayList<Item> itemsList = new ArrayList<>();
    private static final TodoList instance=new TodoList();

    private TodoList() {
    }

    public static TodoList getInstance() {
        return instance;
    }

    public boolean addItem(String title, LocalDate date, String content) {
        return itemsList.add(new Item(title, date, content));
    }


    public boolean removeItem(String title) {
        Optional<Item> removedItem = itemsList.stream()
                .filter(item -> item.title.equalsIgnoreCase(title))
                .findAny();
        return removedItem.map(item -> itemsList.remove(item)).orElse(false);
    }

    public void showList(JspWriter out) throws IOException { //*******we have work with this**********
        out.print("TODO LIST:<br>");
        itemsList.forEach(i-> {
            try {
                out.print(i+"<br>");
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        });
    }


    private static class Item {
        private String title;
        private LocalDate date;
        private String content;

        public Item(String title, LocalDate date, String content) {
            this.title = title;
            this.date = date;
            this.content = content;
        }

        public String getTitle() {
            return title;
        }

        public LocalDate getDate() {
            return date;
        }

        public String getContent() {
            return content;
        }

        @Override
        public String toString() {
            return "title='" + title +
                    ", date=" + date +
                    ", content=" + content+"\n";
        }
    }
}

first output:

Welcome Back! : 2022-05-04
Students with id > 500 :
Hamed
Mohammad
Hossein
TODO LIST:
title='dentist, date=2022-12-23, content=I should go to the dentist
title='park, date=2022-10-01, content=I should go to the Park

second reload:

Welcome Back! : 2022-05-04
Students with id > 500 :
Hamed
Mohammad
Hossein
TODO LIST:
title='dentist, date=2022-12-23, content=I should go to the dentist
title='park, date=2022-10-01, content=I should go to the Park
title='dentist, date=2022-12-23, content=I should go to the dentist
title='park, date=2022-10-01, content=I should go to the Park

third reload:

Welcome Back! : 2022-05-04
Students with id > 500 :
Hamed
Mohammad
Hossein
TODO LIST:
title='dentist, date=2022-12-23, content=I should go to the dentist
title='park, date=2022-10-01, content=I should go to the Park
title='dentist, date=2022-12-23, content=I should go to the dentist
title='park, date=2022-10-01, content=I should go to the Park
title='dentist, date=2022-12-23, content=I should go to the dentist
title='park, date=2022-10-01, content=I should go to the Park

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'output repeats when I reload the page in JSP in Intellij idea

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