我需要帮助在java中更改文本文件

我正在做我的编程入门项目。该程序应该使用一个文本文件作为数据库来存储名字、姓氏和电话号码。程序需要能够操作文本文件上的数据

以下是我到目前为止的全部代码：

import java.util.*;
import java.io.*;
import java.lang.*;
import java.nio.*;

public class Project
{
private static Scanner input;
private static Formatter x;

public static void main(String[] args) 
{
    String choice = "";
    Scanner userInput = new Scanner(System.in);
    System.out.printf("Please choose one of the following commands:%nL (Listing), I (insert), S (search), D (delete)%nM (modify), W (write), Q (quit with saving)");

    loop: while (choice != "Q") {
        System.out.printf("%nEnter your Command: ");
        choice = userInput.nextLine();

        switch (choice)
        {
            case "L":
                Listing();
                break;

            case "I":
                Insert();
                break;

            case "S":
                break;

            case "D":
                break;

            case "M":
                break;

            case "W":
                break;

            case "Q":
                break loop;
        } // end switch statement
    } // end while loop
} // end method main

public static void Listing() // List records from MiniDB.txt file
{
    try {
            File file = new File("MiniDB.txt");
            input = new Scanner(file);
        } 
    catch (IOException ioException) {
     System.err.println("Cannot open file.");
     System.exit(1);
        }
        if (input.hasNext()) { // If there are records in the file print them, else print none found
            while (input.hasNext()) // while there is more to read
            {
                String firstName = input.next();
                String lastName = input.next();
                String phoneNumber = input.next();

            System.out.printf("%-13s%-13s%s%n", firstName + ",", lastName, phoneNumber); }
            }
        else {
            System.out.printf("No records found");
        }
} // end method Listing

public static void Insert() // insert a record
{
    try {
            String file = "MiniDB.txt";
            input = new Scanner(System.in);
            PrintWriter outputStream = new PrintWriter(new FileWriter(file, true) );

            System.out.printf("Last Name: ");
            String lastName = input.next();
            System.out.printf("%nFirst Name: ");
            String firstName = input.next();
            System.out.printf("%nTelephone Number: ");
            String phoneNumber = input.next();

            outputStream.printf("%n%s %s %s", firstName, lastName, phoneNumber);
            outputStream.close();
            System.out.printf("%nDone.");
    } 
    catch (IOException ioException) {
     System.err.println("Cannot open file.");
     System.exit(1);
    }
} // end method Insert

public static void Search(); // search a record
{

}
} // end class Project

我需要的帮助是理解如何创建“write”命令。目前，我的代码自动对文本文件进行更改，但我需要它仅在输入W时完成更改。我已经读了一段时间了，我完全被卡住了。我需要重写我所拥有的吗

---

我正在考虑对temp.txt文件进行所有更改，然后如果输入了W，则重命名temp.txt MiniDB.txt并覆盖该文件。然后我需要删除temp.txt文件。我觉得应该有一个更简单的方法？

对于一个基本的解决方案，为什么不将数据库保存在内存中，然后更新它呢。更新完成后，只需将内存中的版本写入一个文件

即可获得基本解决方案，为什么不将数据库保留在内存中，然后进行更新。更新完成后，只需将内存中的版本写入文件

我怀疑您采取了错误的方法来解决此问题。如果您应该在命令（W）上写入文件，那么最好的解决方案是将数字列表保存在内存中，然后在用户请求时再次写入

比如：

class Entry {
    private String firstName;
    private String lastName;
    private String phoneNumber;
}

List<Entry> entries;

类条目{
私有字符串名；
私有字符串lastName；
私有字符串电话号码；
}
列出条目；

---

当您收到“W”命令时，您可以遍历条目列表并将每个条目写入文件。

我怀疑您采取了错误的方法来解决此问题。如果您应该在命令（W）上写入文件，那么最好的解决方案是将数字列表保存在内存中，然后在用户请求时再次写入

比如：

class Entry {
    private String firstName;
    private String lastName;
    private String phoneNumber;
}

List<Entry> entries;

类条目{
私有字符串名；
私有字符串lastName；
私有字符串电话号码；
}
列出条目；

---

当您收到“W”命令时，您可以遍历条目列表并将每个条目写入文件。

一种方法是使用一些内存对象将数据保持在临时状态 并在完成时将更改写入数据库

我已根据您的要求修改了上述代码 请查收

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

import org.json.JSONException;
import org.json.JSONObject;

public class Project {
    private static Scanner input;
    static JSONObject obj = new JSONObject();
    static String choice = "";
    static int i = 0;
    final static String file_path = "d:\\1\\MiniDB.txt";

    public static void menu() throws IOException, JSONException {
        System.out.println("Please choose one of the following commands:");
        System.out.println("L (Listing)");
        System.out.println("I (Insert)");
        System.out.println("D (delete)");
        System.out.println("S (search)");
        System.out.println("M (modify)");
        System.out.println("W (write)");
        System.out.println("Q (quit with saving)");
        choice = input.nextLine();
        if (choice.equalsIgnoreCase("I")) {
            Insert();
        }
        if (choice.equalsIgnoreCase("L")) {
            Listing();
        }
        if (choice.equalsIgnoreCase("W")) {
            write(obj);
        }
        if (choice.equalsIgnoreCase("Q")) {
            i = 1;
            System.out.println("End");
        }
    }

    public static void main(String[] args) {
        try {
            input = new Scanner(System.in);
            while (i == 0) {
                menu();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void Listing() // List records from MiniDB.txt file
    {
        try {
            File file = new File(file_path);
            input = new Scanner(file);
        } catch (IOException ioException) {
            System.err.println("Cannot open file.");
            System.exit(1);
        }
        if (input.hasNext()) { // If there are records in the file print them,
                                // else print none found
            while (input.hasNext()) // while there is more to read
            {
                String firstName = input.next();
                String lastName = input.next();
                String phoneNumber = input.next();

                System.out.printf("%-13s%-13s%s%n", firstName + ",", lastName,
                        phoneNumber);
            }
        } else {
            System.out.printf("No records found");
        }
    } // end method Listing

    public static void Insert() // insert a record
    {
        try {
            System.out.println("Last Name: ");
            obj.put("Last Name", input.nextLine());
            System.out.println("First Name: ");
            obj.put("First Name", input.nextLine());
            System.out.println("Telephone Number: ");
            obj.put("Telephone Number", input.nextLine());
        } catch (Exception e) {
            System.exit(1);
        }
    }

    public static void write(JSONObject obj2) throws IOException, JSONException {
        File file = new File(file_path);
        PrintWriter outputStream = new PrintWriter(new FileWriter(file, true));
        outputStream.printf("%n%s %s %s", obj.get("Last Name"),
                obj.get("First Name"), obj.get("Telephone Number"));
        System.out.println("changes Done.");
        outputStream.close();
    }

    public static void Search() {
    }

    {
    }
} // end class Project 

我希望这能解决你的问题。

---

非常感谢。快乐编码..

一种方法是使用一些内存对象将数据保持在临时状态 并在完成时将更改写入数据库

我已根据您的要求修改了上述代码 请查收

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

import org.json.JSONException;
import org.json.JSONObject;

public class Project {
    private static Scanner input;
    static JSONObject obj = new JSONObject();
    static String choice = "";
    static int i = 0;
    final static String file_path = "d:\\1\\MiniDB.txt";

    public static void menu() throws IOException, JSONException {
        System.out.println("Please choose one of the following commands:");
        System.out.println("L (Listing)");
        System.out.println("I (Insert)");
        System.out.println("D (delete)");
        System.out.println("S (search)");
        System.out.println("M (modify)");
        System.out.println("W (write)");
        System.out.println("Q (quit with saving)");
        choice = input.nextLine();
        if (choice.equalsIgnoreCase("I")) {
            Insert();
        }
        if (choice.equalsIgnoreCase("L")) {
            Listing();
        }
        if (choice.equalsIgnoreCase("W")) {
            write(obj);
        }
        if (choice.equalsIgnoreCase("Q")) {
            i = 1;
            System.out.println("End");
        }
    }

    public static void main(String[] args) {
        try {
            input = new Scanner(System.in);
            while (i == 0) {
                menu();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void Listing() // List records from MiniDB.txt file
    {
        try {
            File file = new File(file_path);
            input = new Scanner(file);
        } catch (IOException ioException) {
            System.err.println("Cannot open file.");
            System.exit(1);
        }
        if (input.hasNext()) { // If there are records in the file print them,
                                // else print none found
            while (input.hasNext()) // while there is more to read
            {
                String firstName = input.next();
                String lastName = input.next();
                String phoneNumber = input.next();

                System.out.printf("%-13s%-13s%s%n", firstName + ",", lastName,
                        phoneNumber);
            }
        } else {
            System.out.printf("No records found");
        }
    } // end method Listing

    public static void Insert() // insert a record
    {
        try {
            System.out.println("Last Name: ");
            obj.put("Last Name", input.nextLine());
            System.out.println("First Name: ");
            obj.put("First Name", input.nextLine());
            System.out.println("Telephone Number: ");
            obj.put("Telephone Number", input.nextLine());
        } catch (Exception e) {
            System.exit(1);
        }
    }

    public static void write(JSONObject obj2) throws IOException, JSONException {
        File file = new File(file_path);
        PrintWriter outputStream = new PrintWriter(new FileWriter(file, true));
        outputStream.printf("%n%s %s %s", obj.get("Last Name"),
                obj.get("First Name"), obj.get("Telephone Number"));
        System.out.println("changes Done.");
        outputStream.close();
    }

    public static void Search() {
    }

    {
    }
} // end class Project 

我希望这能解决你的问题。

---

非常感谢。快乐编码..

您可以使用相同的json对象执行其他操作您可以使用相同的json对象执行其他操作