显示继承类中的对象数组 [英] Display array of objects from an inheriting class

问题描述

您好，



我试图显示一个对象数组，以便显示对象信息。但是我没有得到正确的结果。结果如下：

[LItem; @ 55f96302

[LItem; @ 55f96302

[LItem; @ 55f96302

[LItem; @ 55f96302

[LItem; @ 55f96302



物品等级：

  private   String  title; 
  private   String 分类; 
  private   String 类型; 
  private   int  ID; 
  private   int  year; 
  private 日历dateLastReturned; 
  private   boolean  available; 
  private  RentItem最新; 
 
  public 项目（ int  ID， int  year， String  title， String 分类，字符串类型）
 {
 此 .ID = ID; 
 此 .year = year; 
 此 .title = title; 
 此 .classification =分类; 
 此 .genre = genre; 
 dateLastReturned = null; 
 available = true; 
 latest = null; 
} 
 
  public  Item（）
 {
 ID =  0 ; 
 year =  0 ; 
 title =  ; 
分类=  ; 
 genre =  ; 
 available = true; 
 dateLastReturned = null; 
 latest = null; 
} 
 
  public   String  getTitle（）{
  return  title; 
} 
 
  public   void  setTitle（ String  title）{
  this  .title = title; 
} 
 
  public   String  getClassification（）{
 返回分类; 
} 
 
  public   void  setClassification（字符串分类）{
 此 .classification = classification; 
} 
 
  public   String  getGenre（）{
  return 类型; 
} 
 
  public   void  setGenre（ String  genre）{
  this  .genre = genre; 
} 
 
  public   int  getID（）{
  return  ID; 
} 
 
  public   void  setID（ int  iD）{
 ID = iD; 
} 
 
  public   int  getYear（）{
 返回年; 
} 
 
  public   void  setYear（ int  year）{
  this  .year = year; 
} 
 
  public 日历getDateLastReturned（）{
  return  dateLastReturned; 
} 
 
  public   void  setDateLastReturned（Calendar dateLastReturned）{
  this  .dateLastReturned = dateLastReturned; 
} 
 
  public   boolean  isAvailable（）{
 返回可用; 
} 
 
  public   void  setAvailable（ boolean  available）{
  this  .available = available; 
} 
 
  public  RentItem getLatest（）{
  return  latest; 
} 
 
  public   void  setLatest（RentItem latest）{
 此 .latest = latest; 
} 
 
  public   void  returnItem（Calendar endDate）
 {
 setDateLastReturned（endDate）; 
 available = true; 
} 
 
  public   String  toString（）
 {
 字符串 str =  ; 
 str = str +   ID： + ID +   \ n +  年份： +年+   \ n +  标题： + title +   \ n +  分类： +分类+   \ n +  类型： + genre +   \ n; 
 str = str +  返回日期： + retDay +   / + retMonth +   / + retYear +   \ n +  可用： + available +   \\\
; 
  if （getLatest（）！= null）
 str = str +  最近租期： +   \ t \ t\t\t + getLatest（）。getReference（）; 
  return  str; 
} 

DVD类（此类是Item类的子类）：

  private   int  numberOfDiscs; 
  private   int  filmRunTime; 
  private  字符串字幕; 
 
  public  DVD（ int  ID， int  year， String  title， String 分类，字符串类型， int  numberOfDiscs， int  filmRunTime，字符串字幕）
 {
  this  .numberOfDiscs = numberOfDiscs; 
  this  .filmRunTime = filmRunTime; 
 此 .subtitles =字幕; 
} 
  public  DVD（）
 {
 numberOfDiscs =  0 < /跨度>; 
 filmRunTime =  0 ; 
 subtitles =  ; 
} 
  public   int  getNumberOfDiscs（）{
  return  numberOfDiscs; 
} 
  public   void  setNumberOfDiscs（ int  numberOfDiscs）{
  this  .numberOfDiscs = numberOfDiscs; 
} 
  public   int  getFilmRunTime（）{
 返回 filmRunTime; 
} 
  public   void  setFilmRunTime（ int  filmRunTime）{
  this  .filmRunTime = filmRunTime; 
} 
  public   String  getSubtitles（）{
 返回字幕; 
} 
  public   void  setSubtitles（字符串字幕）{
 此 .subtitles =字幕; 
} 
  @覆盖 
  public  字符串 toString（）{
  return    DVD [numberOfDiscs = + numberOfDiscs +  ，filmRunTime = 
 + filmRunTime +  ，subtitles = + subtitles +  ，getTitle（）= 
 + getTitle（）+   ，getClassification（）= + getClassification（）
 +  ，getGenre（）= + getGenre（）+  ，getID （）= + getID（）
 +  ，getYear（）= + getYear（）+  ，getDateLastReturned（）=  
 + getDateLastReturned（）+  ，isAvailable（）= + isAvailable （）
 +  ，getLatest（）= + getLatest（）+  ，toString（）= 
 +  super  .toString（）+  ，getClass（）= + getClass（）
 +  ，hashCode（）= + hashCode（）+  ]; 
} 

我的尝试：



我尝试过以下方法：

 静态 Item [] productStorage =  new 项[ 2 ]; 

  public   static   void  initialise（）
 {
  //  创建对象 
 DVD dvd1 = 新 DVD（ 1 ，  2010 ， 快门群岛，< span class =code-string>  16， 神秘，惊悚， 1 ， 138 ， 法语，波兰语，英语） ; 
 DVD dvd2 = 新 DVD（ 2 ， 2006 ，  Prestige，  12， 戏剧，神秘， 1 ， 130 ， 英语，德语，法语，西班牙语）; 
 
  //  为数组赋值 
 productStorage [< span class =code-digit> 0 ] = dvd1; 
 productStorage [ 1 ] = dvd2; 
 
  for （ int  i =  0 ; i< productStorage.length; i ++）
 {
 System.out.println（productStorage）; 
} 

}



然而它显示如下：

[LItem; @ 55f96302

[LItem; @ 55f96302





任何帮助将不胜感激

谢谢！

解决方案

您的问题出在本声明中：

引用：

System.out.println（productStorage）;

仔细看看周围的代码，你应该看看 i 指的是......

 for（int i = 0; i< productStorage.length; i ++）
 {
 System。通过out.println（productStorage）; 
} 

你能表明你得到了什么吗？



我认为你只是保留了你在构造函数中提供的三个值...

 public DVD（int ID，int year，String title，String classification，String genre，int numberOfDiscs，int filmRunTime，String subtitles）
 {
 this.numberOfDiscs = numberOfDiscs; 
 this.filmRunTime = filmRunTime; 
 this.subtitles =字幕; 
} 
 

这意味着这些是唯一可以打印的内容......其余的（ID，年份标题，分类，类型）从未分配过，因此它们将为null / default值。

Hello,

I was trying to display an array of objects so that it will show object information. However I did not get the right result. The result looked like this:
[LItem;@55f96302
[LItem;@55f96302
[LItem;@55f96302
[LItem;@55f96302
[LItem;@55f96302

Item class:

private String title;
	private String classification;
	private String genre;
	private int ID;
	private int year;
	private Calendar dateLastReturned;
	private boolean available;
	private RentItem latest;
	
	public Item(int ID, int year, String title, String classification, String genre)
	{
		this.ID = ID;
		this.year = year;
		this.title = title;
		this.classification = classification;
		this.genre = genre;
		dateLastReturned = null;
		available = true;
		latest = null;
	}
	
	public Item()
	{
		ID = 0;
		year = 0;
		title = "";
		classification = "";
		genre = "";
		available = true;
		dateLastReturned = null;
		latest = null;
	}

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getClassification() {
		return classification;
	}

	public void setClassification(String classification) {
		this.classification = classification;
	}

	public String getGenre() {
		return genre;
	}

	public void setGenre(String genre) {
		this.genre = genre;
	}

	public int getID() {
		return ID;
	}

	public void setID(int iD) {
		ID = iD;
	}

	public int getYear() {
		return year;
	}

	public void setYear(int year) {
		this.year = year;
	}

	public Calendar getDateLastReturned() {
		return dateLastReturned;
	}

	public void setDateLastReturned(Calendar dateLastReturned) {
		this.dateLastReturned = dateLastReturned;
	}

	public boolean isAvailable() {
		return available;
	}

	public void setAvailable(boolean available) {
		this.available = available;
	}

	public RentItem getLatest() {
		return latest;
	}

	public void setLatest(RentItem latest) {
		this.latest = latest;
	}
	
	public void returnItem(Calendar endDate)
	{
		setDateLastReturned(endDate);
		available = true;
	}

	public String toString() 
	{
		String str = "";
		str= str + "ID: "+ID + "\n"+"Year: "+year+"\n"+"Title: "+title+"\n"+"Classification: "+ classification+"\n"+"Genre: "+genre+"\n";
		str = str +"Return Date: "+retDay+"/"+retMonth+"/"+retYear+"\n"+"Available: "+available+"\n";
		if (getLatest() != null)
			str = str + "Most Recent Rental:"+"\t\t\t\t" +getLatest().getReference();
		return str;
	}

DVD class(This class is the subclass of the Item class):

private int numberOfDiscs;
	private int filmRunTime;
	private String subtitles;
	
	public DVD(int ID, int year, String title, String classification, String genre, int numberOfDiscs, int filmRunTime, String subtitles)
	{
		this.numberOfDiscs = numberOfDiscs;
		this.filmRunTime = filmRunTime;
		this.subtitles = subtitles;
	}
	public DVD()
	{
		numberOfDiscs = 0;
		filmRunTime = 0;
		subtitles = "";
	}
	public int getNumberOfDiscs() {
		return numberOfDiscs;
	}
	public void setNumberOfDiscs(int numberOfDiscs) {
		this.numberOfDiscs = numberOfDiscs;
	}
	public int getFilmRunTime() {
		return filmRunTime;
	}
	public void setFilmRunTime(int filmRunTime) {
		this.filmRunTime = filmRunTime;
	}
	public String getSubtitles() {
		return subtitles;
	}
	public void setSubtitles(String subtitles) {
		this.subtitles = subtitles;
	}
	@Override
	public String toString() {
		return "DVD [numberOfDiscs=" + numberOfDiscs + ", filmRunTime="
				+ filmRunTime + ", subtitles=" + subtitles + ", getTitle()="
				+ getTitle() + ", getClassification()=" + getClassification()
				+ ", getGenre()=" + getGenre() + ", getID()=" + getID()
				+ ", getYear()=" + getYear() + ", getDateLastReturned()="
				+ getDateLastReturned() + ", isAvailable()=" + isAvailable()
				+ ", getLatest()=" + getLatest() + ", toString()="
				+ super.toString() + ", getClass()=" + getClass()
				+ ", hashCode()=" + hashCode() + "]";
	} 

What I have tried:

I have tried the following:

static Item[] productStorage= new Item[2];

public static void initialise()
	{
		//creating objects
		DVD dvd1 = new DVD(1, 2010, "Shutter Islands", "16", "Mystery, Thriller", 1, 138, "French, Polish, English");
		DVD dvd2 = new DVD(2, 2006, "Prestige", "12", "Drama, Mystery", 1, 130, "English, German, French, Spanish");

//Assigning value to the array
		productStorage[0] = dvd1;
		productStorage[1] = dvd2;

for(int i = 0; i < productStorage.length; i++)
		{
			System.out.println(productStorage);
		}

}

However it displays it like that:
[LItem;@55f96302
[LItem;@55f96302


Any help will be appreciated
Thanks!

解决方案

Your problem is in this statement:

Quote:

System.out.println(productStorage);

Look carefully at the code around it and you should see what i am referring to...

for(int i = 0; i < productStorage.length; i++)
		{
			System.out.println(productStorage);
		}

Can you show what you are getting?

What I think it is though is you are only keeping three of the values you are providing in the constructor...

public DVD(int ID, int year, String title, String classification, String genre, int numberOfDiscs, int filmRunTime, String subtitles)
{
    this.numberOfDiscs = numberOfDiscs;
    this.filmRunTime = filmRunTime;
    this.subtitles = subtitles;
}

which means these are the only things that will print... the rest (ID, year title, classification, genre) never assigned so they will be null/default values.

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