這是提示：-從ArrayList中獲取一個Iterator并將其分配給局部變量。-使用Iterator遍歷ArrayList，并將Iterator的next方法返回的每個CreditCardNumber的toString寫入輸出文件。（您這次不需要寫任何標簽。）這就是我到目前為止所擁有的。我在寫入文件時遇到了麻煩： public static void writeArr(ArrayList<CreditCardNumber> temp) { FileOutputStream outFile = null; try { outFile = new FileOutputStream("/Users/raska/Desktop/prog6.txt"); } catch (FileNotFoundException e) { System.err.println(e); return; } // end catch Iterator<CreditCardNumber> iter = temp.iterator(); PrintWriter prtWriter = new PrintWriter(outFile, true); while (iter.hasNext()) { CreditCardNumber obj = iter.next(); prtWriter.println(obj); }}這是我對ArrayList的輸入： public static ArrayList<CreditCardNumber> userInputArrList() { System.out.println("Enter the number of elements in the array: "); int arrLength = scanner.nextInt(); if (arrLength < 1) { arrLength = 1; } ArrayList<CreditCardNumber> aList = new ArrayList<CreditCardNumber>(arrLength); for (int i = 0; i < arrLength;) { try { System.out.println("Enter an issuer ID# (6 digits) for element #" + i); String issuerId = scanner.next(); System.out.println("Enter an account # (9 digits) for element #" + i); String accountNum = scanner.next(); CreditCardNumber obj = new CreditCardNumber(issuerId, accountNum); obj.changeId(issuerId); aList.add(obj); i++; } catch (IllegalArgumentException e) { System.out.println(e.toString()); // don't throw just // print } } return aList;}
1 回答
小唯快跑啊
TA貢獻1863條經(jīng)驗 獲得超2個贊
問題是，您永遠不會close()選擇PrintWriter或FileOutputStream。
在方法結束時，請執(zhí)行以下操作：
try {
prtWriter.close();
catch (IOException e) {
// Do some error reporting.
e.printStackTrace();
}
更好的方法是使用Java的try-with資源語句：
public static void writeArr(ArrayList<CreditCardNumber> temp) {
try (FileOutputStream outFile = new FileOutputStream("/Users/raska/Desktop/prog6.txt")) {
Iterator<CreditCardNumber> iter = temp.iterator();
PrintWriter prtWriter = new PrintWriter(outFile, true);
while (iter.hasNext()) {
CreditCardNumber obj = iter.next();
prtWriter.println(obj);
}
} catch (IOException e) {
System.err.println(e);
return;
}
}
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