while循环在第一个错误之后反复返回错误

Question

在一个while循环中，我使循环在一个无效输入后不会返回有效答案，并重复“错误！无效的客户类型，请重试。一遍又一遍，直到我关闭程序。如果我第一次输入R或C作为输入，它可以正常工作。当我输入其他内容时，我收到错误消息“错误！无效的客户类型，请重试。”就像我应该是故意的那样。然而，在输入r或c后，错误再次给我提供了错误，并且我所做的任何输入都会一遍又一遍地返回错误消息，直到关闭程序。有人可以告诉我什么是错的，在我的代码造成这种情况？

public static String getValidCustomerType(Scanner sc) 
{ 
    String customerType = (""); 
     System.out.println("Enter the Customer Type"); 
     customerType = sc.next() ; 
     boolean isValid = false; 
     while (isValid == false) 
     { 
     if (customerType.equalsIgnoreCase("R")|customerType.equalsIgnoreCase("C")) 
     { 
     isValid = true; 
     } 
     else 
     { 
      System.out.println("Error! Invalid customer type. Try again "); 
     } 
     sc.nextLine() ; 
     } 
    return customerType ; 
} 

Answer 1

您不会在while循环内分配给customerType。更好地将其推向一开始。

public static String getValidCustomerType(Scanner sc) 
{ 
    String customerType = (""); 

     boolean isValid = false; 
     while (isValid == false) 
     { 
      System.out.println("Enter the Customer Type"); 
      customerType = sc.nextLine() ; 
     if (customerType.equalsIgnoreCase("R")|customerType.equalsIgnoreCase("C")) 
     { 
     isValid = true; 
     } 
     else 
     { 
      System.out.println("Error! Invalid customer type. Try again "); 
     } 
     } 
    return customerType ; 
} 

Answer 2

我想你必须在while循环内部移动输入呼叫。否则，customerType变量总是相同的。

public static String getValidCustomerType(Scanner sc) 
{ 
    String customerType = (""); 
     System.out.println("Enter the Customer Type"); 
     // move this to while loop 
     //customerType = sc.next() ; 
     boolean isValid = false; 
     while (isValid == false) 
     { 
     // get input here 
     customerType = sc.next() ; 
     if (customerType.equalsIgnoreCase("R")|customerType.equalsIgnoreCase("C")) 
     { 
     isValid = true; 
     } 
     else 
     { 
      System.out.println("Error! Invalid customer type. Try again "); 
     } 
     sc.nextLine() ; 
     } 
    return customerType ; 
} 

Answer 3

试试这个：|（按位OR）是不一样的||这是一个OR运算符。其次，你不再分配customerType - 修正如下。

while (isValid == false) 
    { 
    if (customerType.equalsIgnoreCase("R")||customerType.equalsIgnoreCase("C")) 
    { 
    isValid = true; 
    } 
    else 
    { 
     System.out.println("Error! Invalid customer type. Try again "); 
    } 
    customerType = sc.nextLine() ; 
    } 

Answer 4

我推荐使用带有标记的do while循环。这保证代码至少执行once。

public static String getValidCustomerType(Scanner sc) { 
     String customerType; 
     boolean isValid = false; 

     System.out.println("Enter the Customer Type"); 

     do { 
      customerType = sc.next(); 

      if (customerType.equalsIgnoreCase("R")|customerType.equalsIgnoreCase("C")) { 
       isValid = true; 
      } else { 
       System.out.println("Error! Invalid customer type. Try again "); 
      } 
     } while(!isValid); 

     return customerType ; 
    }