问题描述
每次我传递一个对象来我的数组，它将覆盖previous条目。任何人都可以找出为什么发生这种情况？
addbook（） - 当我把名字和作者它分配一个值，但是当进入另一个标题和作者，它会覆盖previous条目
公共类库{
静态扫描键盘=新的扫描仪（System.in）;
静态诠释计数= 0;
公共静态无效的主要（字串[] args）{
addBook（）;
} //主结束
静态无效addBook（）{
loanbook [] loanArray =新loanbook [5]; 串标题，作者;
INT选择;
布尔onLoan;
loanbook book1的; //测试之用
为（中间体X = 0; X小于5; X ++）{
System.out.print（为小说或2非小说preSS 1：）; //为小说和非小说子菜单
选择= keyboard.nextInt（）;
如果（选择== 1）{ 的System.out.println（请输入书名：）;
标题= keyboard.nextLine（）;
标题= keyboard.nextLine（）;
的System.out.println（请输入书的作者：）;
笔者= keyboard.nextLine（）;
onLoan = FALSE; //尚未使用
BOOK1 =新小说（标题，作者）;
的System.out.println（book1.toString（））;
loanArray [X] =新loanbook（标题，作者）; }
否则，如果（选择== 2）{
的System.out.println（请输入书名：）;
标题= keyboard.nextLine（）;
标题= keyboard.nextLine（）;
的System.out.println（请输入书的作者：）;
笔者= keyboard.nextLine（）;
onLoan = FALSE; //尚未使用
BOOK1 =新纪实（标题，作者）;
的System.out.println（book1.toString（））;
loanArray [X] =新loanbook（标题，作者）;
}
}
}
} //结束图书馆
我Loanbook类
公共类loanbook {
私人字符串标题，作者;
私人诠释BOOKID，计数= 0; 公共loanbook（字符串pTitle，字符串pAuthor）{
BOOKID =计数;
标题= pTitle;
笔者= pAuthor;
算上++;
} //构造函数
公共无效的setTitle（字符串pTitle）{
标题= pTitle;
} //的setTitle
保护串的getTitle（）{
返回称号;
} //的getTitle
保护字符串getAuthor（）{
返回作者;
} // getAuthor
公共字符串的toString（）{
返回的BookID：+ BOOKID +\\ n+标题：+的getTitle（）+\\ n+作者：+ getAuthor（）+\\ n;
}
} // loanbook
您可能希望计数 静态 。我假设你想要的计数每次创建新的预订时间上去。如果没有静态，计数值不会永远持续创建一本书的时间，让你的 BOOKID 将始终为0的每一本书。这的可能的是，为什么你认为的它变得自动覆盖的。我不完全确定，因为你还没有真正解释是什么意思。
私人诠释BOOKID;
公共静态诠释计数= 0; ＆LT; - 静公共loanbook（字符串pTitle，字符串pAuthor）{
BOOKID =计数;
标题= pTitle;
笔者= pAuthor;
算上++;
}
或者更好的，只是避免了计数变量。你做同样的，你会使用计数。因此，计数是不必要的。
公共静态INT BOOKID 0;公共loanbook（字符串pTitle，字符串pAuthor）{
标题= pTitle;
笔者= pAuthor;
BOOKID ++;
}
另外，我不知道你打算用 loanbook BOOK1什么; ，但它用在循环每一次，所以我可以看到这是可能的它覆盖掉了的问题。假设小说和纪实延长 loanbook
此外，我不认为有必要为计数库中的类。你可以摆脱这一点。
更新：
假设你想要的小说或纪实书（他们都扩展 loanbook）在 loanArray`可能你想这样的事情
loanbook书=新小说（标题，作者）;
的System.out.println（book1.toString（））;
loanArray [X] =书;
Every time i pass an object to my array, it overwrites the previous entry. Can anybody spot why this is happening?
addbook() - when i put in name, and author it assigns a value , but when enter another title and author, it overwrites the previous entry.
public class library {
static Scanner keyboard = new Scanner(System.in);
static int count = 0;
public static void main(String [] args){
addBook();
} // Main end
static void addBook(){
loanbook [] loanArray = new loanbook[5];
String title,author;
int choice;
boolean onLoan;
loanbook book1; // TESTING ONLY
for(int x = 0; x < 5; x++){
System.out.print("Press 1 for Fiction or 2 for Non Fiction: "); // sub menu for fiction and non fiction
choice = keyboard.nextInt();
if (choice == 1){
System.out.println("Please enter book title: ");
title = keyboard.nextLine();
title = keyboard.nextLine();
System.out.println("Please enter book author: ");
author = keyboard.nextLine();
onLoan = false; // not used yet
book1 = new fiction(title,author);
System.out.println(book1.toString());
loanArray[x] = new loanbook(title,author);
}
else if (choice == 2) {
System.out.println("Please enter book title: ");
title = keyboard.nextLine();
title = keyboard.nextLine();
System.out.println("Please enter book author: ");
author = keyboard.nextLine();
onLoan = false; // not used yet
book1 = new nonfiction(title,author);
System.out.println(book1.toString());
loanArray[x] = new loanbook(title,author);
}
}
}
} // Library end
My Loanbook class
public class loanbook {
private String title,author;
private int bookID, count = 0;
public loanbook(String pTitle,String pAuthor){
bookID = count;
title = pTitle;
author = pAuthor;
count++;
} // Constructor
public void setTitle(String pTitle){
title = pTitle;
} // setTitle
protected String getTitle(){
return title;
} // getTitle
protected String getAuthor(){
return author;
} // getAuthor
public String toString(){
return " BookID: "+ bookID+"\n" + " Title: "+ getTitle()+"\n" +" Author : "+ getAuthor()+ "\n";
}
} // loanbook
You may want to make count static. I'm assuming you want the count to go up every time a new book is created. Without the static, the count value will not persist ever time a book is created, so your bookID will always be 0 for every book. That may be why you think "it's getting overwriten". I'm not totally sure because you haven't really explained what that means.
private int bookID;
public static int count = 0; <-- static
public loanbook(String pTitle,String pAuthor){
bookID = count;
title = pTitle;
author = pAuthor;
count++;
}
Or better yet, just avoid the count variable. You do the same as you would with the count. So count is unnecessary.
public static int bookID 0;
public loanbook(String pTitle,String pAuthor){
title = pTitle;
author = pAuthor;
bookId++;
}
Also, I don't know what you're planning to with loanbook book1;, but it is used every time in the loop, so I could see this being the possible "it is getting overwritten" problem. Assuming fiction and nonfiction extend loanbook
Also I don't see a need for the count in the library class. You can get rid of that.
Update:
Assuming you want the fiction or nonfiction book (and they both extend loanbook) in yourloanArray` may you want something like this
loanbook book = new fiction(title,author);
System.out.println(book1.toString());
loanArray[x] = book;
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