我是新程序员，
对于代码的使用，我深感抱歉，但我根本找不到错误。
我正试图创建一个存储输入值的arrayList，但是每次创建第二个实例时，第一个实例都会被覆盖。它确实打印两个实例，但是两个实例具有相同的值。
主块： 问题区域位于此代码的底部，“ switch sc1”和“ switch s2，case 2”
package com.company;
import java.io.FileNotFoundException;
import java.util.Scanner;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
public class Main {
public static void main(String[] args) throws FileNotFoundException {
User user = new User(null, null, null, null, null);
Login login = new Login(null, null, null, null, null);
Stream stream = new Stream(null, null, null, null, 0, null, null);
List list = new List(null, null, null, null, 0, null, null);
ArrayList<Stream> joinableList = new ArrayList<Stream>();
ArrayList<Stream> completedList = new ArrayList<Stream>();
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd/MM-yyyy HH:mm");
boolean showRoom = false;
while (showRoom == false) {
System.out.println("\nWelcome to ShowRoom\n\nPress 1 to login\nPress 2 to create a user\n");
Scanner choice1 = new Scanner(System.in);
System.out.print("Input: ");
int s1 = choice1.nextInt();
switch (s1) {
case 1:
System.out.print("\nEnter Username: ");
Scanner scanUsername = new Scanner(System.in);
String username = scanUsername.nextLine();
user.setUsername(username);
System.out.print("\nEnter Password: ");
Scanner scanPassword = new Scanner(System.in);
String password = scanPassword.nextLine();
user.setPassword(password);
login.verifyLogin(username, password);
break;
case 2:
System.out.print("\nChoose Username: ");
Scanner scanChooseUsername = new Scanner(System.in);
username = scanChooseUsername.nextLine();
user.setUsername(username);
user.saveUsername();
System.out.print("\nChoose Password: ");
Scanner scanChoosePassword = new Scanner(System.in);
password = scanChoosePassword.nextLine();
user.setPassword(password);
user.savePassword();
break;
}
boolean loggedIn = false;
while (loggedIn == false) {
System.out.println("\nWelcome to your dashboard " + user.username + "\n\nPress 1 to create a stream\nPress 2 to view joinable streams\nPress 3 to view completed streams");
Scanner choice2 = new Scanner(System.in);
System.out.print("\nInput: ");
int s2 = choice2.nextInt();
switch (s2) {
case 1:
String listUsername = user.username;
stream.setListUsername(user.username);
Scanner chooseTitle = new Scanner(System.in);
System.out.print("\nChoose title: ");
String title = chooseTitle.nextLine();
stream.setTitle(title);
System.out.println("\nYou have chosen: " + stream.title);
Scanner chooseGenre = new Scanner(System.in);
System.out.print("\nChoose genre:\n\nPress 0 for " + stream.genreArray[0] + "\nPress 1 for " + stream.genreArray[1] + "\nPress 2 for " + stream.genreArray[2] + "\n\nInput: ");
int chosenGenre = chooseGenre.nextInt();
String genre = stream.genreArray[chosenGenre];
stream.setGenre(genre);
System.out.println("\nYou have chosen: " + stream.genre);
Scanner chooseType = new Scanner(System.in);
System.out.print("\nChoose type:\n\nPress 0 for " + stream.typeArray[0] + "\nPress 1 for " + stream.typeArray[1] + "\nPress 2 for " + stream.typeArray[2] + "\n\nInput: ");
int chosenType = chooseType.nextInt();
String type = stream.typeArray[chosenType];
stream.setType(type);
System.out.println("\nYou have chosen: " + stream.type);
Scanner choosePrice = new Scanner(System.in);
System.out.print("\nChoose price: ");
double price = choosePrice.nextDouble();
stream.setPrice(price);
System.out.println("\nYou have chosen: " + stream.price);
Scanner chooseStartTimeDate = new Scanner(System.in);
System.out.print("\nChoose start time and date: \n\nInsert time and date in this format: dd/mm-yyyy hh:mm\n\nInput: ");
String startTimeDate = chooseStartTimeDate.nextLine();
stream.setStartTimeDate(startTimeDate);
System.out.println("\nYou have chosen " + stream.startTimeDate);
Scanner chooseEndTimeDate = new Scanner(System.in);
System.out.print("\nChoose end time and date: \n\nInsert time and date in this format: dd/mm-yyyy hh:mm\n\nInput: ");
String endTimeDate = chooseEndTimeDate.nextLine();
stream.setEndTimeDate(endTimeDate);
System.out.println("\nYou have chosen " + stream.endTimeDate);
Scanner confirmStream = new Scanner(System.in);
System.out.print("\nDo you want to create a stream, with the following details?\n\nTitle: " + title + "\nGenre: " + genre + "\nType: " + type + "\nPrice: " + price + "\nStart date and time: " + startTimeDate + "\nEnd date and time: " + endTimeDate + "\n\nPress 1 to confirm\nPress 2 to go back\n\nInput: ");
int sc1 = confirmStream.nextInt();
switch (sc1) {
case 1:
list.addJoinableList(stream);
System.out.println("\nStream has been created and added to list");
loggedIn = false;
break;
case 2:
loggedIn = false;
break;
}
case 2:
list.printJoinableList();
break;
case 3:
System.out.println("\nCompleted stream list");
break;
}
}
}
}
}
流块： 此块用于继承在“列表”类中使用的属性
package com.company;
import java.time.LocalDateTime;
public class Stream {
protected String listUsername;
protected String title;
protected String genre;
protected String type;
protected double price;
protected String startTimeDate;
protected String endTimeDate;
public Stream (String listUsername, String title, String genre, String type, double price, String startTimeDate, String endTimeDate) {
this.listUsername = listUsername;
this.title = title;
this.genre = genre;
this.type = type;
this.price = price;
this.startTimeDate = startTimeDate;
this.endTimeDate = endTimeDate;
}
String genreArray[] = {"Comedy", "Lifestyle", "Music"};
String typeArray[] = {"Entertainment", "Familiy", "Work"};
public String getListUsername() { return listUsername; }
public void setListUsername(String listUsername) { this.listUsername = listUsername; }
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getGenre() {
return genre;
}
public void setGenre(String genre) {
this.genre = genre;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String getStartTimeDate() {
return startTimeDate;
}
public void setStartTimeDate(String startTimeDate) {
this.startTimeDate = startTimeDate;
}
public String getEndTimeDate() { return endTimeDate; }
public void setEndTimeDate(String endTimeDate) { this.endTimeDate = endTimeDate;}
}
列表块： 我认为主要问题就在这里，但我只是想不出什么错。
package com.company;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
public class List extends Stream {
public List(String listUsername, String title, String genre, String type, double price, String startTimeDate, String endTimeDate) {
super(listUsername, title, genre, type, price, startTimeDate, endTimeDate);
}
ArrayList<Stream> joinableList = new ArrayList<Stream>();
ArrayList<Stream> completedList = new ArrayList<Stream>();
public void addJoinableList(Stream stream) {
joinableList.add(stream);
}
public void printJoinableList() {
for (Stream s : joinableList) {
System.out.print("\nUsername: " + s.getListUsername());
System.out.print("\nTitle: " + s.getTitle());
System.out.print("\nGenre: " + s.getGenre());
System.out.print("\nType: " + s.getType());
System.out.print("\nPrice: " + s.getPrice());
System.out.print("\nStart time and date: " + s.getStartTimeDate());
System.out.print("\nEnd time and date: " + s.getEndTimeDate() + "\n");
}
}
}
感谢所有帮助，谢谢。
答案 0 :(得分：3)
当我看到这样创建的对象一次：
User user = new User(null, null, null, null, null);
然后，没有new User，我了解到您从不创建对象的新实例。
其余的代码是一样的：（几乎）您只创建一个对象实例，而不是一个新实例。
因此，当您更改所述实例的属性时，它将影响所有对象。
您需要在代码中添加一个位置，当您感觉到用户输入的数据（并由Scanner读取）时，可以创建一个新的User，{{1} }，...
例如，在此之后：
Stream要做：
list.addJoinableList(stream);