在Windows中创建FileInputStream时出现错误
deletebook()方法。但是相同的对象创建在
searchBook()方法。没有人知道为什么当唯一不同的是传递给方法的参数时，代码会产生不同的结果吗？
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
public class TestMain {
public static final String FILENAME = "cool_file.txt";
public static void main(String[] args) throws IOException, ClassNotFoundException {
// TODO Auto-generated method stub
FileOutputStream fos = null;
fos = new FileOutputStream(FILENAME);
System.out.println("Welcome to the Application");
ObjectOutputStream oos1;
int sel = 0;
TestMain t = new TestMain();
do {
System.out.println("1) addSubject");
System.out.println("2) addBook");
System.out.println("3) deleteSubject");
System.out.println("4) deleteBook");
System.out.println("5) searchBook");
System.out.println("6) searchSubject");
System.out.println("7) Exit");
System.out.println("#############");
System.out.println("Insert a selection");
Scanner s = new Scanner(System.in);
sel = s.nextInt();
switch (sel) {
case 1:
t.addSubject();
break;
case 2:
t.addBook(fos);
break;
case 3:
t.deleteSubject();
break;
case 4:
t.deleteBook(fos);
break;
case 5:
t.searchBook();
break;
case 6:
t.searchSubject();
break;
case 7:
t.exitService();
break;
default:
System.out.println("Invalid Selection");
}
} while (sel != 7);
}
public void addSubject() {
System.out.println("In addSubject"+"\n");
}
public void addBook(FileOutputStream fos) throws IOException {
System.out.println("In addBook"+"\n");
long bookId;
String title;
double price;
Integer volume;
LocalDate publishDate;
ObjectOutputStream oos = new ObjectOutputStream(fos);
System.out.println("Enter Book ID");
Book b=new Book();
Scanner s=new Scanner(System.in);
bookId=s.nextLong();
System.out.println("Enter the Title of the Book");
title=s.next();
System.out.println("Enter the price of the Book");
price=s.nextDouble();
System.out.println("Enter the Volume of the Book");
volume=s.nextInt();
System.out.println("Enter the publishDate of the Book");
String dateStr_1=s.next();
DateTimeFormatter formatter_1=DateTimeFormatter.ofPattern("dd-MM-yyyy");
publishDate= LocalDate.parse(dateStr_1,formatter_1);
b.setBookId(bookId);
b.setTitle(title);
b.setPrice(price);
b.setVolume(volume);
b.setPublishDate(publishDate);
oos.writeObject(b);
//fos.close();
//oos.close();
}
public void deleteSubject() {
System.out.println("In deleteSubject"+"\n");
}
public void deleteBook(FileOutputStream fos) throws IOException, ClassNotFoundException {
System.out.println("In deleteBook"+"\n");
System.out.println("Enter the Book Id to be deleted");
Scanner s=new Scanner(System.in);
int bookId=s.nextInt();
ArrayList<Book> results = new ArrayList<Book>();
FileInputStream fis = null;
System.out.println(fis);
try {
fis = new FileInputStream(FILENAME);
System.out.println(fis);
while (true) {
ObjectInputStream ois = new ObjectInputStream(fis);
results.add((Book) ois.readObject());
}
} catch (EOFException ignored) {
ignored.printStackTrace();
// as expected
} finally {
if (fis != null)
fis.close();
System.out.println("Finally");
}
System.out.println("results = " + results);
for(Book b:results)
{
if(b.getBookId()==bookId)
{
results.remove(b);
}
}
File file = new File(FILENAME);
if(file.exists())
{
file.delete();
System.out.println("File Exists");
if(file.exists())
{
System.out.println("File Exists after deletion");
}
}
if(file.delete())
{
System.out.println("File deleted successfully");
}
else
{
System.out.println("Failed to delete the file");
}
/*ObjectOutputStream oos = new ObjectOutputStream(fos);
for(Book newb:results)
oos.writeObject(newb);*/
}
public void searchBook() throws ClassNotFoundException, IOException {
System.out.println("In searchBook"+"\n");
ArrayList<Book> results = new ArrayList<Book>();
FileInputStream fis = null;
try {
fis = new FileInputStream(FILENAME);
while (true) {
ObjectInputStream ois = new ObjectInputStream(fis);
results.add((Book) ois.readObject());
}
} catch (EOFException ignored) {
// as expected
} finally {
if (fis != null)
fis.close();
}
System.out.println("results = " + results);
}
public void searchSubject() {
System.out.println("In searchSubject"+"\n");
}
public void exitService() {
System.out.println("Thank You for using the service..You rare now Exitinng the service");
}
}
这是控制台：
欢迎来到应用程序1）addSubject 2）addBook 3）deleteSubject 4）deleteBook 5）searchBook 6）searchSubject 7）退出
#######在addBook中插入选择2输入图书ID 1输入图书标题ufihv输入价格 书籍1输入书籍的体积1输入书籍的出版日期 图书01-01-2001 1）addSubject 2）addBook 3）deleteSubject 4） deleteBook 5）searchBook 6）searchSubject 7）退出
#######在addBook中插入选择2输入书籍ID 2输入书籍的标题2输入书籍的价格 图书2输入图书的体积2输入图书的发布日期 图书02-02-2002 1）addSubject 2）addBook 3）deleteSubject 4） deleteBook 5）searchBook 6）searchSubject 7）退出
#######插入选择4在deleteBook中输入要删除的图书ID 1空 java.io.FileInputStream@7106e68e java.io.EOFException最终结果 = [Book @ 1a6c5a9e，Book @ 37bba400]文件存在删除后文件存在删除文件失败1）addSubject 2）addBook 3） deleteSubject 4）deleteBook 5）searchBook 6）searchSubject 7）退出
#######在java.io.ObjectInputStream $ PeekInputStream.readFully插入选择（未知源）at java.io.ObjectInputStream $ BlockDataInputStream.readShort（未知 源）位于java.io.ObjectInputStream.readStreamHeader（未知源） 在java.io.ObjectInputStream（未知来源）在 TestMain.deleteBook（TestMain.java:124）在 TestMain.main（TestMain.java:49）
答案 0 :(得分：0)
我不太确定，为什么要删除具有对象可序列化状态的文件。因此，当您删除文件时，该文件具有对象的可序列化状态。您将丢失所有内容，即使文件不存在。而且，如果您尝试通过其他方法访问同一文件，则会出现异常。
此外，删除特定对象时，不会将对象的最新更新状态保存到文件中（未序列化对象的最新状态），而是直接删除了文件。那么，从反序列化对象中删除对象有什么意义呢？