無限循環java

Question

問題規範：無限循環（菜單進入無限循環）;

目標：請求用戶輸入一個整數，然後按照指定的邏輯進行編碼。如何避免無限循環？

代碼：

public Purchase groceryStoreMenu(LemonadeStand lemonadeStand){ 

    boolean getMenu = true; 
    int userEnteredNumber = -1; 
    currentPurchase = new Purchase(); 

    while(getMenu){ 
     try{ 

      System.out.println("Grocery Store"); 
      System.out.printf("%s\t%s%n%s\t%s%n%s\t%s%n%s\t%s%n%s\t%s%n%s\t%s%n" , "1:" , "Buy lemons", "2:", "Buy cups" , "3:" , "Buy sugar" , 
      "4:" , "Buy ice" , "5:" , "Done"); //change this 
      userEnteredNumber = reader.nextInt(); 

      if (userEnteredNumber == 1) { 
       money = lemonadeStand.profit(0); 
       lemonsMenu(money); 
      }else if (userEnteredNumber == 2){ 
       money = lemonadeStand.profit(0); 
       cupsMenu(money); 
      }else if (userEnteredNumber == 3){ 
       money = lemonadeStand.profit(0); 
       sugarMenu(money); 
      }else if (userEnteredNumber == 4){ 
       money = lemonadeStand.profit(0); 
       iceMenu(money); 

      }else{ 
       money = lemonadeStand.profit(0); 
      dailyGreetingMenu(); 

      } 

     if (userEnteredNumber != 1 && userEnteredNumber !=2 && userEnteredNumber != 3 
      && userEnteredNumber != 4 && userEnteredNumber != 5) { 
    throw new Exception(); 
    } else if(userEnteredNumber == 6) { 
     getMenu = false; 
     //break; 
    } else { 
     getMenu = false; 
     //break; 
    } 

    } 

    catch(Exception e) 
    { 
     System.out.println("Error in number format. Enter a valid number from the choices (1,2,3,4,5,6)"); 
    } 

    } 


    return currentPurchase; 

Answer 1

你的計劃從未達到if(userEnteredNumber == 6) 6價值，因爲如果userEnteredNumber是6，第一個條件會抓住它：

if (userEnteredNumber != 1 && userEnteredNumber !=2 && userEnteredNumber != 3 
     && userEnteredNumber != 4 && userEnteredNumber != 5) { 
    throw new Exception(); 
} 

那麼它會拋出異常，它在循環塊內編輯爲catch。除了1,2,3,4,5,6以外的任何數字都是相同的。所以循環永遠不會結束。

我不喜歡你的代碼風格。但如果你想這樣做，你應該添加userEnteredNumber != 6第一條件。

Answer 2

看起來像執行是永遠不會進入下面的塊： else if（userEnteredNumber == 6）{ getMenu = false; // break; }

如果條件不應該包含「& &」。它應該是「||」 也看起來像你不想讓你的用戶輸入除1,2,3,4,5以外的任何數字。

if (userEnteredNumber != 1 || userEnteredNumber !=2 || userEnteredNumber != 3 
     || userEnteredNumber != 4 || userEnteredNumber != 5) { 
    getMenu = false;    
    throw new Exception(); 
}