java - 尝试让我的数组列表打印给定的项目

Question

我正在尝试获取用 Java 创建的联系人列表。我想我已经拥有了大部分，尽管我确信它可以得到增强。我相信我可以将项目添加到数组列表中，但是，当我尝试打印数组列表时，我得到了一些随机文本和数字。另外，我并没有迷失通过联系人 ID 号码进行识别，然后只是打印该联系人。任何帮助或引用 Material 都会有很大帮助!我尝试过阅读教科书并在网上进行研究，说实话，现在我只是更困惑了。这是我的代码:主要:

package contactslist;
import java.util.*;
import java.io.*;
public class ContactsList {
public static void main(String[] args) {
    Scanner input1 = new Scanner(System.in);
    int type = 0;
    ArrayList<Contacts> contacts = new ArrayList<Contacts>();
    while(type != 4){
    System.out.println("[1] Personal Contact");
    System.out.println("[2] Business Contact");
    System.out.println("[3] Display Contacts");
    System.out.println("[4] to quit");
    type = input1.nextInt();
    if(type == 4){
        System.out.println("Goodbye");
        break;
        }
    else if (type == 3){
        int totalContacts = contacts.size();
        for (int i = 0; i < totalContacts; i++){
            System.out.print(contacts);
        }
    }
    Scanner inputs = new Scanner(System.in);
    System.out.println("Please enter a numeric ContactId: ");
    String contactId = inputs.nextLine();
    System.out.println("Please enter First Name: ");
    String firstName = inputs.nextLine();
    if (firstName == null) {
        break;
    }
    System.out.println("Please enter Last Name: ");
    String lastName = inputs.nextLine();
    if (lastName == null) {
        break;
    }
    System.out.println("Please enter Address: ");
    String address = inputs.nextLine();
    System.out.println("Please enter Phone Number: ");
    String phoneNumber = inputs.nextLine();
    System.out.println("Please enter Email Address: ");
    String emailAddress = inputs.nextLine();
    if(type == 1){
       System.out.println("Please enter Birthday: ");
       String dateofBirth = inputs.nextLine();
       Contacts personal = new PersonalContact(contactId, firstName, lastName, address,
phoneNumber, emailAddress, dateofBirth);
       contacts.add(personal);
    }
    else if(type == 2){
        System.out.println("Please enter Job Title: ");
        String jobTitle = inputs.nextLine();
        System.out.println("Please enter Organization: ");
        String organization = inputs.nextLine();
        Contacts business = new BusinessContact(contactId, firstName, lastName,
address, phoneNumber, emailAddress, jobTitle, organization);
        contacts.add(business);
    }
    }
    }
    }  

联系人类别:

package contactslist;
import java.util.*;
import java.io.*;
public abstract class Contacts {
String contactId;
String firstName;
String lastName;
String address;
String phoneNumber;
String emailAddress;
public Contacts(String contactId,String firstName,String lastName, String address,
String phoneNumber, String emailAddress)
{
    this.contactId = contactId;
    this.firstName = firstName;
    this.lastName = lastName;
    this.address = address;
    this.phoneNumber = phoneNumber;
    this.emailAddress = emailAddress;
}
public void setContactId(String input){
    this.contactId = input;
}
public String getContactId(){
    return contactId;
}
public void setFirstName(String input){
    this.firstName = input;
}
public String getFirstName(){
    return firstName;
}
public void setLastName(String input){
    this.lastName = input;
}
public String getLastName(){
    return lastName;
}
public void setAddress(String input){
    this.address = input;
}
public String getAddress(){
    return address;
}
public void setPhoneNumber(String input){
    this.phoneNumber = input;
}
public String getPhoneNumber(){
    return phoneNumber;
}
public void setEmailAddress(String input){
    this.emailAddress = input;
}
public String getEmailAddress(){
    return emailAddress;        
}
public void displayContacts(){
    System.out.println("Contact ID: " + contactId + " First Name: " + firstName + "
Last Name: " + lastName);
}
}

个人子类:

package contactslist;
import java.util.*;
import java.io.*;
public class PersonalContact extends Contacts{
private String dateofBirth;
public PersonalContact(String contactId, String firstName, String lastName, String
address, String phoneNumber, String emailAddress, String dateofBirth){
super(contactId, firstName, lastName, address, phoneNumber, emailAddress);
this.dateofBirth = dateofBirth;
}
public void setDateofBirth(String input){
this.dateofBirth=input;
}
public String getDateofBirth(){
return this.dateofBirth;
}
@Override
public void displayContacts(){
System.out.print("Personal Contacts: ");
System.out.println("Contact ID: " + contactId + " First Name: " + firstName + " Last
Name: " + lastName);
System.out.println("Address: " + address);
System.out.println("Phone Number: " + phoneNumber);
System.out.println("Email Address: " + emailAddress);
System.out.println("Birthday: " + dateofBirth); 
}
}

业务子类:

package contactslist;
public class BusinessContact extends Contacts{
private String jobTitle;
private String organization;
public BusinessContact(String contactId, String firstName, String lastName, String
address, String phoneNumber, String emailAddress, String jobTitle, String organization)
{
super(contactId, firstName, lastName, address, phoneNumber, emailAddress);
this.jobTitle = jobTitle;
this.organization = organization;
}
public void jobTitle(String input){
this.jobTitle = jobTitle;
}
public String getjobTitle(){
return this.jobTitle;
}
public void organization(String input) {
this.organization = organization;
}
public String getOrganization(){
return this.organization;
}
@Override
public void displayContacts(){
System.out.print("Personal Contacts: ");
System.out.println("First Name: " + firstName + " Last Name :" + lastName);
System.out.println("Address: " + address);
System.out.println("Phone Number: " + phoneNumber);
System.out.println("Email Address: " + emailAddress);
System.out.println("Job Title: " + jobTitle);
System.out.println("Orgnanization: " + organization);
}   
}

以下是当我选择选项 3 以显示联系人时打印的内容。

错误:

[contactslist.PersonalContact@1df38fd]

任何帮助将不胜感激。我快疯了，请原谅我的问题。我尝试了一些不同的东西，我在谷歌上搜索过，但我就是不明白。有人能给我指出正确的方向，或者给我一个好的网站可供引用吗？

Answer 1

您需要编写自己的方法来打印该 ArrayList。类似于:

public void printAllContacts(ArrayList<Contacts> contacts) {
    for (Contacts c : contacts) {
      c.displayContacts();
    }
}

并调用它来代替选项 3 的 System.out.println(contacts); (Java 将只打印有关该对象的信息)。

在这里阅读有关 ArrayList 的更多信息:https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html