用户输入验证的所有可能性

Question

我想确保用户只输入一个int，并且范围从10到20
当我第一次输入一个超出范围的int时，我最终得到一个错误然后输入一个字符串。我不确定如何继续要求用户继续输入，直到数字落在指定的范围内。 任何帮助，将不胜感激！

public static void main(String[] args) { 

    Scanner scnr = new Scanner(System.in); 

    int width = 0; 
    int height = 0; 

    System.out.println("Welcome to Mine Sweeper!"); 
    System.out.println("What width of map would you like (10 - 20): "); 
    //width = scnr.nextInt() 
    while (!scnr.hasNextInt()) { 
     System.out.println("Expected a number from 10 to 20"); 
     scnr.next(); 
    } 
    do { 
     width = scnr.nextInt(); 
     if (width < 10 || width > 20) { 
      System.out.println("Expected a number from 10 to 20"); 
      //width = scnr.nextInt(); 
     } 
    } while (width < 10 || width > 20); 
} 

Answer 1

试试这个：

Scanner scnr = new Scanner(System.in); 

    int width = 0; 
    int height = 0; 

    System.out.println("Welcome to Mine Sweeper!"); 
    while(true) 
    { 
     System.out.println("What width of map would you like (10 - 20): "); 
     try{ 
      width = scnr.nextInt(); 
      System.out.println(width); 
      if (width < 10 || width > 20) 
      { 
       System.out.println("Expected a number from 10 to 20"); 
      } 
      else 
       break; 
     }catch(Exception e) 
     { 
      System.out.println("Expected a number from 10 to 20"); 
      scnr.next(); 
     } 
    } 
    scnr.close(); 

Answer 2

这应该做你想要什么：

while (scnr.hasNext()) { 
    if (scnr.hasNextInt()) { 
     width = scnr.nextInt(); 
     if (width >= 10 && width <= 20) { 
      break; 
     } 
    }else{ 
     scnr.next(); 
    } 
    System.out.println("Expected a number from 10 to 20"); 
} 
System.out.println("width = " + width); 

Answer 3

据我了解，你是想只接受的范围之间的整数值10和20包括在内。如果输入了字符或字符串，则需要打印出一条消息并继续执行。如果是这样，那么这应该接近你想要的。我原本打算用try-catch声明来回答这个问题，但我注意到你回答了另一个答案，并说你想要一个与使用try-catch不同的方法。此代码不是100％功能;你将不得不调整一些东西，但它非常接近你正在寻找的东西，我认为没有使用try-catch声明。

public static void main(String args[]) 
{ 
    Scanner scanner = new Scanner(System.in); 
    int width = 0; 
    int height = 0; 
    int validInput = 0; //flag for valid input; 0 for false, 1 for true 

    System.out.println("Welcome to Mine Sweeper!"); 
    System.out.println("What width of map would you like (10 - 20): "); 

    while (validInput == 0) //while input is invalid (i.e. a character, or a value not in range 
    { 
     if (scanner.hasNextInt()) 
     { 
      width = scanner.nextInt(); 
      if (width >= 10 && width <= 20) 
      { 
       validInput = 1; //if input was valid 
      } 
      else 
      { 
       validInput = 0; //if input was invalid 
       System.out.println("Expected a number from 10 to 20."); 
      } 
     } 
     else 
     { 
      System.out.println("You must enter integer values only!"); 
      validInput = 0; //if input was invalid 
     } 
     scanner.next(); 
    } 
}