錯誤：變量digitMonth可能未被初始化

Question

我正試圖編寫一個程序，該程序需要出生年份，月份和日期，並計算哪一天說的生日說謊。事情是，我收到此錯誤消息：

錯誤：變量digitMonth可能未初始化 total = inputYear + test2 + digitMonth + inputDay; ^

我不知道如何解決它。將digitMonth設置爲一個數字（例如1）可以使程序正常工作，但對於公式，每個月需要一個不同的數字（1月1日，4月2月，4月3月，0月4月等）

我看過其他問題，發現了這樣的錯誤，但我還沒有發現任何有用的東西。

幫助？

import java.util.Scanner; 
public class Birth{ 

public static void main(String[] args) 
{ 
    Scanner scan = new Scanner(System.in); 
    int inputYear, inputMonth, inputDay, digitMonth, test2, total, dayNum; 

    System.out.println("Enter the last two digits of the year that you were born in"); 
    inputYear = scan.nextInt(); 
    System.out.println("Enter the month number that your were born in"); 
    inputMonth = scan.nextInt(); 
    System.out.println("Enter your birth day"); 
    inputDay = scan.nextInt(); 

    test2 = inputYear/4; 

    if (inputMonth > 0 && inputMonth < 2) 
    { 
     digitMonth = 1; 
    } 
    else if (inputMonth > 1 && inputMonth < 3) 
    { 
      digitMonth = 4; 
    } 
    else if (inputMonth > 2 && inputMonth < 4) 
    { 
      digitMonth = 4; 
    } 
    else if (inputMonth > 3 && inputMonth < 5) 
    { 
      digitMonth = 0; 
    } 
    else if (inputMonth > 4 && inputMonth < 6) 
    { 
      digitMonth = 2; 
    } 
    else if (inputMonth > 5 && inputMonth < 7) 
    { 
      digitMonth = 5; 
    } 
    else if (inputMonth > 6 && inputMonth < 8) 
    { 
      digitMonth = 0; 
    } 
    else if (inputMonth > 7 && inputMonth < 9) 
    { 
      digitMonth = 3; 
    } 
    else if (inputMonth > 8 && inputMonth < 10) 
    { 
      digitMonth = 6; 
    } 
    else if (inputMonth > 9 && inputMonth < 11) 
    { 
      digitMonth = 1; 
    } 
    else if (inputMonth > 10 && inputMonth < 12) 
    { 
      digitMonth = 4; 
    } 
    else if (inputMonth > 11 && inputMonth < 13) 
    { 
      digitMonth = 6; 
    } 
    else 
     System.out.println("You fuck-up"); 


    total = inputYear + test2 + digitMonth + inputDay; 
    dayNum = total/7; 

    if (dayNum > 0 || dayNum < 2) 
    { 
     System.out.println("You were born on a Sunday"); 
    } 
    else if (dayNum > 1 || dayNum < 3) 
    { 
     System.out.println("You were born on a Monday"); 
    } 
    else if (dayNum > 2 || dayNum < 4) 
    { 
     System.out.println("You were born on a Tuesday"); 
    } 
    else if (dayNum > 3 || dayNum < 5) 
    { 
     System.out.println("You were born on a Wednesday"); 
    } 
    else if (dayNum > 4 || dayNum < 6) 
    { 
     System.out.println("You were born on a Thursday"); 
    } 
    else if (dayNum > 5 || dayNum < 7) 
    { 
     System.out.println("You were born on a Friday"); 
    } 
    else if (dayNum > -1 || dayNum < 1) 
    { 
     System.out.println("You were born on a Saturday"); 
    } 
} 

}

Answer 1

你只分配if和else if語句中，而不是在最後else語句值digitMonth。
那麼如果if和else if都沒有成功並且只有else部件會發生什麼情況？
The 那麼digitMonth的值會是什麼呢？

答案：無

這可能永遠不會發生在你的代碼中，但編譯器會抱怨它。

有2級的解決方案：

1）只要給一個初始值digitMonth。即int digitMonth = 0;

2）在最後else中初始化digitMonth。即：

else{ 
    //some code 
    digitMonth = 0; 
} 

希望這有助於

Answer 2

在你的代碼，這是一個可能性，前值賦給它，digitMonth使用。一種選擇是設置digitMonth爲缺省值：

int digitMonth = 0; 

另一種方法是在else分支值賦給digitMonth：

... 
else { 
    System.out.println("Invalid month"); 
    digitMonth = 0; 
} 

你也可以停在else分支的控制流：

... 
else { 
    return; 
    // OR throw a RuntimeException 
    // throw new IllegalArgumentException 
} 

Answer 3

您需要初始化digitMonth到zero以及 我認爲這是不正確的邏輯在你的代碼太：

你應該有：dayNum = total % 7;

希望下面的代碼工作正常：

public static void main(String args[]) { 

     Scanner scan = new Scanner(System.in); 
     int inputYear, inputMonth, inputDay, digitMonth = 0, test2, total, dayNum; 

     System.out.println("Enter the last two digits of the year that you were born in"); 
     inputYear = scan.nextInt(); 
     System.out.println("Enter the month number that your were born in"); 
     inputMonth = scan.nextInt(); 
     System.out.println("Enter your birth day"); 
     inputDay = scan.nextInt(); 

     test2 = inputYear/4; 

     if (inputMonth > 0 && inputMonth < 2) 
     { 
      digitMonth = 1; 
     } 
     else if (inputMonth > 1 && inputMonth < 3) 
     { 
       digitMonth = 4; 
     } 
     else if (inputMonth > 2 && inputMonth < 4) 
     { 
       digitMonth = 4; 
     } 
     else if (inputMonth > 3 && inputMonth < 5) 
     { 
       digitMonth = 0; 
     } 
     else if (inputMonth > 4 && inputMonth < 6) 
     { 
       digitMonth = 2; 
     } 
     else if (inputMonth > 5 && inputMonth < 7) 
     { 
       digitMonth = 5; 
     } 
     else if (inputMonth > 6 && inputMonth < 8) 
     { 
       digitMonth = 0; 
     } 
     else if (inputMonth > 7 && inputMonth < 9) 
     { 
       digitMonth = 3; 
     } 
     else if (inputMonth > 8 && inputMonth < 10) 
     { 
       digitMonth = 6; 
     } 
     else if (inputMonth > 9 && inputMonth < 11) 
     { 
       digitMonth = 1; 
     } 
     else if (inputMonth > 10 && inputMonth < 12) 
     { 
       digitMonth = 4; 
     } 
     else if (inputMonth > 11 && inputMonth < 13) 
     { 
       digitMonth = 6; 
     } 
     else 
      System.out.println("You fuck-up"); 


     total = inputYear + test2 + digitMonth + inputDay; 
     dayNum = total % 7; 

     switch(dayNum){ 
     case 1:System.out.println("You were born on a Sunday");break; 
     case 2:System.out.println("You were born on a Monday");break; 
     case 3: System.out.println("You were born on a Tuesday");break; 
     case 4:System.out.println("You were born on a Wednesday");break; 
     case 5:System.out.println("You were born on a Thursday");break; 
     case 6:System.out.println("You were born on a Friday");break; 
     case 7:System.out.println("You were born on a Saturday");break; 

     }