java创建一个可以增删改查的记事本程序

A：

思路：

1. 创建一个文本文件，用于存储记事本中记录的内容。

2. 设计菜单，允许用户选择要执行的操作。

3. 根据用户输入的操作选择，执行相应的方法。

4. 编写增删改查的具体逻辑。

代码实现：

import java.util.Scanner;
import java.io.*;

public class NotePad {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        String fileName = "note.txt";

        while (true) {
            //1.显示菜单
            System.out.println("Menu: ");
            System.out.println("1.添加记录");
            System.out.println("2.删除记录");
            System.out.println("3.修改记录");
            System.out.println("4.查找记录");
            System.out.println("5.退出");

            //2.让用户选择
            System.out.print("请输入要执行的操作：");
            int choice = sc.nextInt();

            switch (choice) {
                case 1:
                    addRecord(fileName);
                    break;
                case 2:
                    deleteRecord(fileName);
                    break;
                case 3:
                    modifyRecord(fileName);
                    break;
                case 4:
                    searchRecord(fileName);
                    break;
                case 5:
                    System.exit(0);//退出程序
                default:
                    System.out.println("输入有误，请重新输入！");
                    break;
            }
        }
    }

    //添加记录
    public static void addRecord(String fileName) {
        Scanner sc = new Scanner(System.in);
        BufferedWriter bw = null;
        try {
            File file = new File(fileName);
            bw = new BufferedWriter(new FileWriter(file, true));

            System.out.print("请输入要添加的内容：");
            String content = sc.nextLine();
            bw.write(content);
            bw.newLine();//换行
            bw.flush();

            System.out.println("添加成功！");

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (bw != null) {
                try {
                    bw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    //删除记录
    public static void deleteRecord(String fileName) {
        Scanner sc = new Scanner(System.in);
        BufferedReader br = null;
        BufferedWriter bw = null;

        try {
            File file = new File(fileName);
            File tempFile = new File("temp.txt");
            br = new BufferedReader(new FileReader(file));
            bw = new BufferedWriter(new FileWriter(tempFile));

            System.out.print("请输入要删除的内容：");
            String content = sc.nextLine();
            String line;

            while ((line = br.readLine()) != null) {
                if (line.equals(content)) {
                    System.out.println("删除成功！");
                    continue;
                }
                bw.write(line);
                bw.newLine();
            }

            file.delete();
            tempFile.renameTo(file);//重命名

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (br != null) {
                    br.close();
                }
                if (bw != null) {
                    bw.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    //修改记录
    public static void modifyRecord(String fileName) {
        Scanner sc = new Scanner(System.in);
        BufferedReader br = null;
        BufferedWriter bw = null;
        try {
            File file = new File(fileName);
            File tempFile = new File("temp.txt");
            br = new BufferedReader(new FileReader(file));
            bw = new BufferedWriter(new FileWriter(tempFile));

            System.out.print("请输入要修改的内容：");
            String oldContent = sc.nextLine();

            System.out.print("请输入新内容：");
            String newContent = sc.nextLine();

            String line;
            while ((line = br.readLine()) != null) {
                if (line.equals(oldContent)) {
                    bw.write(newContent);
                } else {
                    bw.write(line);
                }
                bw.newLine();
            }

            file.delete();
            tempFile.renameTo(file);//重命名

            System.out.println("修改成功！");

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (br != null) {
                    br.close();
                }
                if (bw != null) {
                    bw.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    //查找记录
    public static void searchRecord(String fileName) {
        Scanner sc = new Scanner(System.in);
        BufferedReader br = null;

        try {
            File file = new File(fileName);
            br = new BufferedReader(new FileReader(file));

            System.out.print("请输入要查找的内容：");
            String content = sc.nextLine();

            String line;
            boolean flag = false;
            while ((line = br.readLine()) != null) {
                if (line.equals(content)) {
                    System.out.println("找到了这条记录：" + line);
                    flag = true;
                }
            }
            if (flag == false) {
                System.out.println("没有找到这条记录！");
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (br != null) {
                    br.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}