try-catch不會捕獲IOException

Question

在下面的代碼中，我獲得了Unreachable catch block for IOException的Unreachable catch block for IOException 。 永遠不會從try語句體錯誤（帶下划線）拋出此異常，其中IOException位於} catch (IOException e){我做錯了什么？

class driver {

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    Customer forrest = new Customer("Forrest Gump", 1,
        "42 New Street, New York, New York");
    Customer random = new Customer("Random Name", 2,
        "44 New Street, New York, New York");
    Customer customer[] = { null, forrest, random };
    int whichOption = 1;
    int id = 0;
    char action = ' ';
    char accSrc = ' ';
    char accDest = ' ';
    double amount = 0;
    BankAccount src = null;
    do {

      try{
        // process JOptionPane input information
        String input = JOptionPane
            .showInputDialog("Please enter your transaction information: ");
        Scanner s = new Scanner(input);
        id = Integer.parseInt(s.next());
        action = Character.toUpperCase((s.next().charAt(0)));

        if (action == 'T') {
          amount = s.nextDouble();
          accSrc = s.next().charAt(0);
          accDest = s.next().charAt(0);
        } else if (action == 'G' || action == 'I') {
          accSrc = s.next().charAt(0);
        } else {
          // if D,W
          amount = s.nextDouble();
          accSrc = s.next().charAt(0);
        }

      } catch (IOException e){

      }
      // taking action accordingly (T)ransfer, (D)eposit, (W)ithdraw, (I)nterest
      if (action == 'T') {

        (customer[id].getAccount(accSrc)).transfer(amount,
            customer[id].getAccount(accDest));
      } else if (action == 'G') {
        System.out.println("The current balance on your " + accSrc
            + " account is "
            + customer[id].getAccount(accSrc).getBalance() + "\n");
      } else if (action == 'D') {
        (customer[id].getAccount(accSrc)).deposit(amount);
      } else if (action == 'W') {
        (customer[id].getAccount(accSrc)).withdraw(amount);
      } else if (action == 'I') {
        (customer[id].getAccount(accSrc)).computeInterest();
      }
      whichOption = JOptionPane
          .showConfirmDialog(null , "Do you want to continue?");

      System.out.println("The balance on " + customer[id].getName()
          + " auto account is " + customer[id].A.balance);
      System.out.println("The balance on " + customer[id].getName()
          + " savings account is " + customer[id].S.balance);
      System.out.println("The balance on " + customer[id].getName()
          + " checkings account is " + customer[id].C.balance);
      System.out.println("The balance on " + customer[id].getName()
          + " loan account is " + customer[id].L.balance + "\n");

    } while (whichOption == 0);

  }
}

Answer 1

這是因為你在try/catch執行的操作都沒有拋出IOException。

根據Scanner javadoc

大多數Scanner類方法拋出FileNotFoundException （由於不從文件中讀取，因此不適用於您的情況）（或） IllegalArgumentException （或） IllegalStateException

您需要將IOException更改為上述任一異常（或）刪除try / catch。

Answer 2

您可以刪除IOException和try catch，因為try catch中的所有語句都不會拋出此異常

Answer 3

在try塊中拋出IOException似乎沒什么

Answer 4

在try塊中沒有方法調用拋出IOException ，這就是catch是無法訪問的代碼的原因。

您可以安全地刪除try和catch，因為這種情況永遠不會發生。

Answer 5

你的catch塊是空的，表明你無論如何都不會真正處理異常。 你可能在那里有一些代碼讓你抓住它，但現在你已經沒有它了。 只需刪除整個周圍的try-catch ，就不會有其他問題。

Answer 6

try/catch塊為空，代碼不會拋出IOException但它可能拋出其他異常。