我有麻烦了。我想知道如何修复它约2个小时,我什么都不知道。你能帮助我吗? 我已经再次编写了这段代码,但它没有改变任何东西,仍然不知道我在哪里犯错。getSize期间出现NullPointerException
public class Historia {
public ArrayList<String> tablica;
public void odczyt() throws IOException, ClassNotFoundException {
ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("skarbonka.bin"));
tablica = (ArrayList<String>) objectInputStream.readObject();
objectInputStream.close();
int size = tablica.size();
for(int i = 0; i<size; i++){
System.out.println(tablica.get(i));
}
}
有二类:
public class Zapis {
private GregorianCalendar gregorianCalendar = new GregorianCalendar();
private Scanner scanner = new Scanner(System.in);
private Historia dodaj = new Historia();
public void plik() throws IOException {
Dane dane = new Dane();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("skarbonka.bin"));
ArrayList<String> arrayList = new ArrayList<String>();
dane.kwota = scanner.nextInt();
dane.dzien = String.format("%tc", gregorianCalendar);
int g = dodaj.tablica.size();
for(int i=0; i<g; i++){
arrayList.add("");
arrayList.set(i, dodaj.tablica.get(i));
}
arrayList.add(dane.toString());
objectOutputStream.writeObject(arrayList);
objectOutputStream.close();
}
}
任何想法?感谢帮助!
它必须是一个存钱罐,它显示我的帐户状态和当天发生了变化。 感谢您的帮助,但现在我注意到下一个差距。我的输入只显示最后一项。为什么?我想(int i = 0; i