爲什麼`if（guess！='a'|| guess！='A'|| ...）`不起作用？

Question

這裏是我的代碼，我知道if語句很長，代碼可能會更有效率，但我只是想知道這個答案，因爲它會讓我瘋狂。

while (whileloop == 1) 
    { 
    if (guess != 'a' || guess != 'A' || guess != 'b' || guess != 'B' || guess != 'c' || guess != 'C' || guess != 'd' || guess != 'D' || guess != 'e' || guess != 'E' || guess != 'f' || guess != 'F' || guess != 'g' || guess != 'G' || guess != 'h' || guess != 'H' || guess != 'i' || guess != 'I' || guess != 'j' || guess != 'J' || guess != 'k' || guess != 'K' || guess != 'l' || guess != 'L' || guess != 'm' || guess != 'M' || guess != 'n' || guess != 'N' || guess != 'o' || guess != 'O' ||guess != 'p' || guess != 'P' || guess != 'q' || guess != 'Q' || guess != 'r' || guess != 'R' || guess != 's' || guess != 'S' || guess != 't' || guess != 'T' || guess == ' ') 
    { 
     System.out.println ("\nNot a Point. Try again."); 
     guess = IBIO.inputChar ("If the missile is launched from Point B, which Point will the missile hit? "); 
    } 
    else 
     whileloop = 2; 
    } 

Answer 1

因爲你想要一個合乎邏輯的和&&（不是邏輯或||）。如果任何條件爲true（例如字母A不是字母B，整個表達式爲真），則使用||。你可以使用帶有兩個ands的||。類似於

if (!(guess >= 'a' && guess <= 'z') || !(guess >= 'A' && guess <= 'Z'))