java loop，if else

Question

我知道這是非常簡單的事情，但是，我只編程了幾個月，所以我的大腦有時會霧化出來，我需要一個帶有嵌套else if語句的while循環的幫助。問題我的循環是連續的，因爲用戶從來沒有機會進入他們的選擇（-1停止循環）。我怎樣才能改變循環，讓它通過要求用戶輸入一個選項（1-4或-1退出）來操作

請任何幫助表示讚賞。我知道這很簡單，我已經通過以前的論壇討論進行過搜索，但我似乎無法使其工作。

//create new scanner object 
    Scanner userInput = new Scanner (System.in); 
    int end = 0; 
    //find out what user wants to do with address book 
    while (end != -1) 
    { 
     System.out.println(" "); 
     System.out.println(" "); 
     System.out.println("----------------------------"); 
     System.out.println("What would you like to do with your address book? ..."); 
     System.out.println("----------------------------"); 
     System.out.println("Add new   [Enter 1]"); 
     System.out.println("Delete existing [Enter 2]"); 
     System.out.println("Edit existing [Enter 3]"); 
     System.out.println("Search for  [Enter 4]"); 
     System.out.println("EXIT   [Enter -1]"); 
    } 

    if (userInput.hasNext() && (userInput.nextInt() == 1)) 
    { 
     AddressBookProcessor.addContact(); 
    } 
    else if (userInput.hasNext() && userInput.nextInt() == 2) 
    { 
     AddressBookProcessor.deleteContact(); 
    } 
    else if (userInput.hasNext() && userInput.nextInt() == 3) 
    { 
     AddressBookProcessor.editContact(); 
    } 
    else if (userInput.hasNext() && userInput.nextInt() == 4) 
    { 
     AddressBookProcessor.findContact(); 
    } 
    else if (userInput.nextInt() != 1 || userInput.nextInt() != 2 
        || userInput.nextInt() != 3 || userInput.nextInt() != -1) 
    { 
     System.out.println("Please enter a valid input"); 
     end = -1; 
    } 




} 

Answer 1

你不改變while循環內的end變量，這樣的結果在一個無限循環。您需要將輸入處理邏輯放在while循環中，以便end有機會更改，以便while循環可以結束。

Answer 2

將你的if/else移到while循環中。

Answer 3

簡單地把如果在循環中聲明應該工作（注意，我還沒有籤任何東西上的代碼，這只是一個快速響應）：

//create new scanner object 
    Scanner userInput = new Scanner (System.in); 
    int end = 0; 
    //find out what user wants to do with address book 
    while (end != -1) 
    { 
     System.out.println(" "); 
     System.out.println(" "); 
     System.out.println("----------------------------"); 
     System.out.println("What would you like to do with your address book? ..."); 
     System.out.println("----------------------------"); 
     System.out.println("Add new   [Enter 1]"); 
     System.out.println("Delete existing [Enter 2]"); 
     System.out.println("Edit existing [Enter 3]"); 
     System.out.println("Search for  [Enter 4]"); 
     System.out.println("EXIT   [Enter -1]"); 
    if (userInput.hasNext() && (userInput.nextInt() == 1)) 
    { 
     AddressBookProcessor.addContact(); 
    } 
    else if (userInput.hasNext() && userInput.nextInt() == 2) 
    { 
     AddressBookProcessor.deleteContact(); 
    } 
    else if (userInput.hasNext() && userInput.nextInt() == 3) 
    { 
     AddressBookProcessor.editContact(); 
    } 
    else if (userInput.hasNext() && userInput.nextInt() == 4) 
    { 
     AddressBookProcessor.findContact(); 
    } 
    else if (userInput.nextInt() != 1 || userInput.nextInt() != 2 
        || userInput.nextInt() != 3 || userInput.nextInt() != -1) 
    { 
     System.out.println("Please enter a valid input"); 
     end = -1; 
    } 
    } 

}