Question

我创建了一个while循环来为我的程序创建一个菜单，它会一直循环，直到用户在控制台中输入'Quit'。我的问题是，无论何时我在控制台中输入'Transfer'，if语句都会完美运行，但当它返回循环开始时，System.out.println();消息会打印两次而不是一次。任何其他选项都不会发生这种情况。

代码：

int x = 0;
while(x != 1) {
    System.out.println("To transfer funds, please type 'Transfer'\n" //Typical message
                + "To list recent transactions, please type 'Recent'\n"
                + "To display account details, please type 'Details'\n"
                + "To quit the application, please type 'Quit'");

    String Option1 = "Transfer"; //Variables
    String Option2 = "Recent"; 
    String Option3 = "Details";
    String Option4 = "Quit";
    String Menu = ConsoleInput.nextLine();

    if (Menu.equals(Option1)) {
            //Statements
    } else if(Menu.equals(Option2)){
            //Statements
    } else if(Menu.equals(Option3)){
            //Statements
    } else if(Menu.equals(Option4)){
            //End statement
            x++;
    }
}

编辑：有些人正在评论最后一个else语句中x的增量，并说它应该放在else语句之外。它就在那里，因为当用户在控制台中键入“Quit”时它将退出循环，如果它被放在else语句之外，那么用户将无法访问其他选项。

编辑2（解决方案）：我终于解决了问题。原来它是if语句中的扫描程序语句。我应该已经显示了所有人都可以看到的完整代码，但我认为这只是if-else语句本身。

Answer 1

需要注意的几件事情：

您应该Menu.equalsIgnoreCase(Option1)等。
你应该在while循环之后加上x的增量。除非输入End，否则永远不会递增x。

我认为你真的想要更像

private static String[] options = {"Transfer","Recent","Details","Quit"};
private static int C_Transfer = 0;
private static int C_Recent = 1;
private static int C_Details = 2;
private static int C_Quit = 3;
private static int[] optionCase = {C_Transfer, C_Recent, C_Details,C_Quit);
private String menu;
private String message = "To transfer funds, please type 'Transfer'\n" //Typical message
                + "To list recent transactions, please type 'Recent'\n"
                + "To display account details, please type 'Details'\n"
                + "To quit the application, please type 'Quit'"

System.out.println(message);
menu = ConsoleInput.nextLine()
while (!menu.equalsIgnoreCase(options[C_Quit]) {
    int case = -1;
    for (int i=0, i < options.length; i++) {
      if (menu.equalsEgnoreCase(options[i]) {
          case = i;
          break;
      }
      switch (case) 
        case C_Transfer: {
           break;
        } 
        case C_Transfer: {
           break;
        } 
        case C_Transfer: {
           break;
        } 
        case C_Transfer: {
           break;
        }
        default: { 
           System.out.println(message);
        }
        Menu = ConsoleInput.nextLine();
     }
}

Answer 2

这只发生在转移选项上吗？你能展示一下转移选项的代码吗？可能有指令在那里打印消息，所以当循环重新开始时你打印了两次消息。

添加：根据您的转移代码＆＃39;。似乎这个问题与java.util.Scanner的错误使用有关，但我自己也不确定这个实用程序类。但是下面修改后的代码对我有用：

public static void main(String[] args){
        java.util.Scanner ConsoleInput=new java.util.Scanner(System.in);
        String Menu;
        String message="To transfer funds, please type 'Transfer'\n" //Typical message
                + "To list recent transactions, please type 'Recent'\n"
                + "To display account details, please type 'Details'\n"
                + "To quit the application, please type 'Quit'";
        System.out.println(message);
                String Option1 = "Transfer"; //Variables
        String Option2 = "Recent"; 
        String Option3 = "Details";
        String Option4 = "Quit";
        while(!((Menu=ConsoleInput.nextLine()).equalsIgnoreCase(Option4))){
            if(Menu.equalsIgnoreCase(Option1)){
                System.out.println("You have selected transfer");
                System.out.println("How much would you like to transfer?");
                float deduction;
                float total = 2500;
                deduction = ConsoleInput.nextFloat();
                total = total - deduction;
                System.out.println("£" + total + " left in account. Transaction recorded.");
                //Fileoutput.println(sf.format(date) + " - £" + deduction + " taken from account. £" + total + " left in account.\n");  
                System.out.println(message);
            }else if(Menu.equalsIgnoreCase(Option2)){
                System.out.println("here is your balance...blah, blah, bbla\n");
                System.out.println(message);
            }else if(Menu.equalsIgnoreCase(Option3)){
                System.out.println("here is the details...blah, blah, bbla\n");
                System.out.println(message);
            }
        }
        System.out.println("Thanks");
    }

System.out.println（）在while循环期间打印两次

2 个答案: