无法让 Java 执行 while 循环来中断

Question

我的钱包程序有一个简单但令人不满的问题，向我的钱包添加钱时似乎一切正常，但当我输入“-1”作为我的 moneyChoice 时，我似乎无法跳出我的 do-while 循环。

private static void AddItemToWallet()throws IOException{
boolean valid=true;
String input;
int moneyChoice;
char addToWallet;

do{
  out.println("\n\n======================================================");
  do{
    out.println("Please enter choice to add (integer) --->");
    //display money choices
    System.out.println("Avaliable moneys to add:\n");
    for (Money money : Money.values()) {
      System.out.print(money.ordinal()+1 + " --- ");
      System.out.print(money + ": ");
      System.out.println(money.GetDenom());
    }
    //scanner=new Scanner(in);
    moneyChoice=scanner.nextInt();
    if (moneyChoice > 11 || moneyChoice <= -2 || moneyChoice == 0) {
      out.println("Your choice is not valid.");
    } 
  }while(moneyChoice > 11 || moneyChoice <= -2 || moneyChoice ==0);

  out.println(moneyChoice);
  do{
    try{
      valid=false;
      scanner=new Scanner(in);
      //confirm choice
      out.println("Add item to wallet? (y/n)");
      input=scanner.nextLine();
      addToWallet=input.charAt(0);
      if (Character.toLowerCase(addToWallet)=='n'){
        out.println("Selection " + moneyChoice + " was not added to wallet.");
        valid=true;
      }else if (Character.toLowerCase(addToWallet)=='y'){
        out.println("Selection " + moneyChoice + " was added to wallet.");
        valid=true;

        Money money = Money.PENNY; 
        if(moneyChoice ==1){ 
          money = Money.PENNY;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==2){ 
          money = Money.NICKLE;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==3){ 
          money = Money.DIME;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==4){ 
          money = Money.QUARTER;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==5){ 
          money = Money.HALFDOLLAR;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==6){ 
          money = Money.ONE;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==7){ 
          money = Money.FIVE;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==8){ 
          money = Money.TEN;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==9){ 
          money = Money.TWENTY;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==10){ 
          money = Money.FIFTY;
          wallet.add(money.GetDenom());
        }
        if(moneyChoice ==11){ 
          money = Money.HUNDRED;
          wallet.add(money.GetDenom());
        }

        System.out.println(money);



        //Using a Switch and set ENUM
        Money foundMoney = money;
        switch (foundMoney) {
          case PENNY:
            money = Money.PENNY; 
            System.out.println("Pennies are useless");
            break;
          case NICKLE:
            System.out.println("Why did the fan go to the concert? To get their Nickle back!!! Man are they horrible.");
            break;
          case DIME:
            System.out.println("How come Dimes are the smallest coin? So strange.");
            break;
          case QUARTER:
            System.out.println("Tom Brady, best Quarterback eva!!!!");
            break;
          case HALFDOLLAR:
            System.out.println("Half Dollar coin. Have you seen one???");
            break;
          case ONE:
            System.out.println("One is the lonliest number.");
            break;
          case FIVE:
            System.out.println("Five Buck Lunch, here I come!!!");
            break;
          case TEN:
            System.out.println("Ten is what grandma gave you for graduation.");
            break;
          case TWENTY:
            System.out.println("Twenty Bucks. 2 0... awesome.");
            break;
          case FIFTY:
            System.out.println("Fitty Sploondocks.");
            break;
          case HUNDRED:
            System.out.println("I did it for the Benjamins. Get rich or die trying.");
            break;
        }
      }
    }catch(Exception ex){

    }
    if (!valid){
      out.println("That is not a valid answer");
    }
  }while(!valid);  
 }while(moneyChoice!= -1);

}

Answer 1

你的程序基本上可以简化成下面这样

do {
    // read moneyChoice

    do {

         // Perform logic

    } while ( ! valid );

} while ( moneyChoice != -1 );

请注意，在您阅读moneyChoice 之后，您总是进入执行逻辑的do。没有任何东西可以检查您输入的moneyChoice 是否为-1。所以无论如何都会执行逻辑，只有当你点击while ( moneyChoice != -1 )时，它才会停止。

您应该添加一个if，这样只有在读取的moneyChoice 不是-1 时才会执行逻辑。

do {
    // read moneyChoice

    if ( moneyChoice != -1 ) {
        do {

         // Perform logic

        } while ( ! valid );
    }

} while ( moneyChoice != -1 );