如何避免Java中的無限循環

Question

我該如何重新編寫此代碼，以便不使用while（true）循環？ 我需要打破while循環條件的方法，但似乎無法解決。

ArrayList<Account> accounts = new ArrayList<Account>();

public void enterCustomers()
{
   System.out.println("Enter customer names or q to quit entering names");

   while(true)
    {
        Scanner scan = new Scanner(System.in);                          //find alternative to while true

        System.out.print("Enter a customer name: ");
        String name = scan.nextLine();

        if(name.equalsIgnoreCase("q"))
        {
            break;
        }

        System.out.print("Enter openning balance: ");
        Double balance = scan.nextDouble();

        Account a = new Account(name, balance);
        accounts.add(a);}
}

Answer 1

因此，如果要刪除while（true）循環，可以使用以下代碼：

String name = scan.nextLine();
while(!name.equalsIgnoreCase("q")){
  //do stuff here
  name = scan.nextLine();
}

或者更好的方法是使用do while循環（避免重復的名稱分配），因為do while將在進入循環后檢查條件：

String name;
do{
  name = scan.nextLine();
  //do stuff here
}while(!name.equalsIgnoreCase("q"));

Answer 2

我認為解決此問題的最簡單方法是將while循環的條件設置為與if條件相反的條件，如下所示：

ArrayList<Account> accounts = new ArrayList<Account>();

public void enterCustomers()
{
   Scanner scan = new Scanner(System.in);
   System.out.println("Enter customer names or q to quit entering names");
   System.out.println("Enter a customer name:");
   Stirng name = scan.nextLine();

   while(!name.equalsIgnoreCase("q"))
    {     
        System.out.print("Enter openning balance: ");
        Double balance = scan.nextDouble();

        Account a = new Account(name, balance);
        accounts.add(a);            

        System.out.print("Enter a customer name: ");
        name = scan.nextLine();
    }
}

Answer 3

首先要知道scan.nextDouble（）正在讀取數字，而不是折線，您必須添加一個虛擬scan.nextLine（）或類似的東西，以讀取數字后的折線。

我總是喜歡讓方法做一件事情，例如askForData（Scanner scan），所以看起來像這樣：

import java.util.Scanner;

public class SomeTest {

public static void main(String[] args) {
    System.out.println("Enter customer names or q to quit entering names");
    Scanner scan = new Scanner(System.in);
    String name="notExit"; //some name that is not exiting
    while(!name.equalsIgnoreCase("q")){
        name = askForData(scan);
    }
}

private static String askForData(Scanner scan) {
    System.out.print("Enter a customer name: ");
    String name = scan.nextLine();
    if (!name.equalsIgnoreCase("q")) {
        System.out.print("Enter openning balance: ");
        Double balance = scan.nextDouble();
        scan.nextLine(); //to read the break line
    }
    return name;
}
}