如果數組中輸入的數據小於零，輸入驗證

Question

我試圖創建一條錯誤消息，該方法允許用戶輸入一年中每個月的降雨量。我試圖阻止數據存儲在數組中。我正在使用do-while循環，但似乎無法弄清楚如何檢查輸入是否小於零。謝謝你們的幫助，歡呼！

public static double[] getRainFall() 
    { 
     double[] rainfallMonths = new double[12]; 
     double[] rainfall = new double[12]; 

     do 
     { 
      for(int x = 0; x < rainfallMonths.length; x++) 
      { 
        System.out.print("What is the rainfall for month #" + (x + 1) + ": "); 
       rainfallMonths[x] = keyboard.nextDouble(); 
       rainfall[x] = rainfallMonths[x]; 

       if(rainfallMonths < 0) 
       { 
        System.out.println("Input is Invalid"); 
       } 
      } 
     }while(rainfallMonths < 0); 


     for(int count = 0; count < rainfallMonths.length; count++) 
     { 
      System.out.println("Rainfall Month #" + (count + 1) + ": " + rainfall[count]); 
     } 

     return rainfall; 
    } 

Answer 1

你的邏輯是有點過，更不要說你想一個數組進行比較的int ......

首先，邏輯......

do 
    for x = 0 to rainfallMonths.length -1 do 
     ... get input... 
while value < 0 

問題在於，您已將輸入分配給for-next循環中的數組的所有元素，但是您試圖驗證在for-next之外輸入的值，該值可能永遠不會返回有效結果。 ..太遲了.. 。

相反，要扭轉邏輯...

for x = 0 to rainfallMonths.length -1 do 
    do 
     value = get input from user 
    while value < 0 
    rainfallMonths[x] = value 

接下來，rainfallMonths是一個數組的引用，這實際上不是要被檢查反對什麼，你需要檢查對一個它的值或元素，例如...

while (rainfallMonths[x] < 0); 

，如果沒有那是有道理的......

public static double[] getRainFall() 
{ 
    double[] rainfallMonths = new double[12]; 
    double[] rainfall = new double[12]; 

    for(int x = 0; x < rainfallMonths.length; x++) 
    { 
     double input = 0; 
     System.out.print("What is the rainfall for month #" + (x + 1) + ": "); 
     do { 
      rainfallMonths[x] = keyboard.nextDouble(); 
      rainfall[x] = rainfallMonths[x]; 
      if(input < 0) 
      { 
       System.out.println("Input is Invalid"); 
      } 
     } while (rainfallMonths[x] < 0);  
    } 


    for(int count = 0; count < rainfallMonths.length; count++) 
    { 
     System.out.println("Rainfall Month #" + (count + 1) + ": " + rainfall[count]); 
    } 

    return rainfall; 
} 

你可能想進修上Arrays這應有助於;）

Answer 2

double temp = -1; 
for(int x = 0; x < rainfallMonths.length; x++) 
     { 
      System.out.print("What is the rainfall for month #" + (x + 1) + ": "); 
      temp = keyboard.nextDouble(); 
      if(temp < 0) 
      { 
       System.out.println("Input is Invalid"); 
       x--; //if you want the user to maybe try to repeat this month again? 
      } 
      else 
      { 
       rainfallMonths[x] = keyboard.nextDouble(); 
       rainfall[x] = rainfallMonths[x]; 
      } 
     }