用java写一个记事本程序，拥有文件打开、保存、编辑、查找的功能

好的，我可以提供一个简单的Java记事本程序的示例代码，具有文件打开、保存、编辑和查找功能。请注意，此代码仅用于学习和参考，有关生产级别代码和安全性的考虑，请参考相关文档和实践。

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

public class Notepad {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String filename = "";
        String line = "";

        while (true) {
            // menu
            System.out.println("Choose an option:");
            System.out.println("1 - Open file");
            System.out.println("2 - Save file");
            System.out.println("3 - Edit file");
            System.out.println("4 - Find text");
            System.out.println("0 - Exit");

            // read option from user input
            int option = scanner.nextInt();
            scanner.nextLine(); // consume the newline character

            switch (option) {
                case 1:
                    // open file
                    System.out.print("Enter filename: ");
                    filename = scanner.nextLine();
                    try {
                        FileReader fileReader = new FileReader(filename);
                        BufferedReader bufferedReader = new BufferedReader(fileReader);

                        while ((line = bufferedReader.readLine()) != null) {
                            System.out.println(line);
                        }

                        bufferedReader.close();
                    } catch (IOException e) {
                        System.out.println("Error reading file: " + e.getMessage());
                    }
                    break;

                case 2:
                    // save file
                    System.out.print("Enter filename: ");
                    filename = scanner.nextLine();
                    try {
                        FileWriter fileWriter = new FileWriter(filename);
                        BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);

                        while (!(line = scanner.nextLine()).equals(":wq")) {
                            bufferedWriter.write(line);
                            bufferedWriter.newLine();
                        }

                        bufferedWriter.close();
                    } catch (IOException e) {
                        System.out.println("Error writing file: " + e.getMessage());
                    }
                    break;

                case 3:
                    // edit file
                    System.out.print("Enter filename: ");
                    filename = scanner.nextLine();

                    // read the file into a StringBuilder object
                    StringBuilder sb = new StringBuilder();
                    try {
                        FileReader fileReader = new FileReader(filename);
                        BufferedReader bufferedReader = new BufferedReader(fileReader);

                        while ((line = bufferedReader.readLine()) != null) {
                            sb.append(line);
                            sb.append(System.lineSeparator());
                        }

                        bufferedReader.close();
                    } catch (IOException e) {
                        System.out.println("Error reading file: " + e.getMessage());
                        break;
                    }

                    // edit the content
                    System.out.println("Edit the content. Enter ':wq' to save and exit.");
                    String content = sb.toString();
                    int index = content.lastIndexOf(System.lineSeparator());
                    System.out.print(content.substring(0, index + 1));
                    String newContent = "";
                    while (!(line = scanner.nextLine()).equals(":wq")) {
                        newContent += line + System.lineSeparator();
                    }
                    newContent += System.lineSeparator();

                    // save the edited content back to the file
                    try {
                        FileWriter fileWriter = new FileWriter(filename);
                        BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);

                        bufferedWriter.write(newContent + content.substring(index + 1));
                        bufferedWriter.close();
                    } catch (IOException e) {
                        System.out.println("Error writing file: " + e.getMessage());
                    }
                    break;

                case 4:
                    // find text
                    System.out.print("Enter filename: ");
                    filename = scanner.nextLine();
                    System.out.print("Enter text to find: ");
                    String text = scanner.nextLine();

                    try {
                        FileReader fileReader = new FileReader(filename);
                        BufferedReader bufferedReader = new BufferedReader(fileReader);

                        int lineNumber = 1;
                        boolean found = false;
                        while ((line = bufferedReader.readLine()) != null) {
                            if (line.contains(text)) {
                                System.out.println("Found at line " + lineNumber + ": " + line);
                                found = true;
                            }
                            lineNumber++;
                        }

                        bufferedReader.close();
                        if (!found) {
                            System.out.println("Text not found in the file.");
                        }
                    } catch (IOException e) {
                        System.out.println("Error reading file: " + e.getMessage());
                    }
                    break;

                case 0:
                    // exit
                    System.out.println("Bye!");
                    System.exit(0);
                    break;

                default:
                    System.out.println("Invalid option. Please choose again.");
                    break;
            }
        }
    }
}

这个程序基于命令行，它可以使用Java的标准输入输出和文件读写API，实现简单的文件处理功能。在文件打开时，可以按行读取文件中的内容并输出到控制台。在文件保存时，可以将用户在命令行输入的内容写入文件中。在文件编辑时，它会先将文件读取到StringBuilder对象中，再在命令行中提示用户输入要编辑的内容。当用户输入“:wq”时，编辑完成，并将所做的更改写回到原始文件中。在查找文件时，可以读取文件并逐行搜索包含指定文本的行。