在方法之間傳遞變量

Question

我正在創建一個具有不同方法的骰子游戲。但是，我似乎無法弄清楚如何在我的方法之間傳遞變量以用於其他方法。它從一個菜單開始，用戶將「選擇」奇數1或2，然後轉到滾動方法以獲得滾動的總和，然後計算方法告訴用戶他們是否有一個或丟失。但是，我似乎無法弄清楚如何傳遞diceSum並在計算方法中使用我的方法之間進行選擇。

我似乎無法弄清楚如何讓select和diceSum在diceCalc（）中用於打印出用戶的答案。

private static void guess(){ 
    Scanner input = new Scanner(System.in); 
    System.out.print("(1) Odd\n" 
      +"(2) Even\n" 
      +"(3) Quit Game\n" 
      +"What is your selection: "); 
    try { 
     int select = input.nextInt(); 
     if(select == 1) { 
      System.out.println(""); 
      diceRoll(); 
     } else if(select == 2) { 
      System.out.println(""); 
      diceRoll(); 
     } else if(select == 3) { 
      System.out.println("Thank you for playing Dueling Dice v1.0..."); 
    system.out(0); 
} 

private static void diceRoll() { 
    int roll1, roll2, diceSum; 
    roll1 = (int)(Math.random()*6+1); 
    roll2 = (int)(Math.random()*6+1); 
    diceSum = roll1 + roll2; 

    System.out.println(" Dice 1 roll = " + roll1); 
    System.out.println(" Dice 2 roll = " + roll2); 
    System.out.println("TOTAL dice roll = " + diceSum); 
    diceCalc(); // this is called in the main after the guess since guess performs the roll 
} 

private static void diceCalc() { 
    if (diceSum % 2 != 0 && select == 1 || diceSum % 2 == 0 && select == 2) { 
     if (select == 1) { 
      System.out.println("Dice rolled = " + diceSum + "and you selected odd"); 
     } else { 
      System.out.println("Dice rolled = " + diceSum + "and you selected even"); 
     } 
     System.out.println("CONGRATULATIONS! You WIN!!"); 
     won++; 
     played++; 
    }else if (diceSum % 2 == 0 && select == 1 || diceSum % 2 != 0 && select == 2){ 
     if (select == 1) { 
      System.out.println("Dice rolled = " + diceSum + "and you selected odd"); 
     } else { 
      System.out.println("Dice rolled = " + diceSum + "and you selected even"); 
     } 
     System.out.println("I am sorry you lost!"); 
     lost++; 
     played++; 
    } 
    System.out.print("it is making it here!"); 

Answer 1

您可以將diceSum傳遞給diceCalc方法。

diceCalc(diceSum); // this is called in the main after the guess since guess performs the roll 

然後將參數添加到diceCalc函數。

private static void diceCalc(int diceSum) 

Answer 2

您可以使用一些在Java中讀取函數和參數。 Check here。

儘管這一點，你可以這樣做：

通行證select參數diceRoll方法

private static void guess(){ 
    int select = <someValue> 
    ... 
    diceRoll(select); 
    ... 
} 

在diceRoll方法，你聲明參數如下圖所示。

private static void diceRoll(int varSelect) { 
    ... 
    System.out.println("Select value: " + varSelect); 
    ... 
} 

編輯1：只要記住，原始類型的Java按值傳遞的，這意味着如果你改變內部diceRoll的varSelect的價值，它不會範圍更新select值方法guess。檢查這個問題：Is Java 「pass-by-reference」 or 「pass-by-value」?

Answer 3

下面是例子：

void methodA(){ 
int toB = 5; 
methodB(toB); 
} 
void methodB(int fromA){ 
int recievedFromA = fromA; 
System.out.println(recievedFromA); 
} 

什麼書或課程您使用的？ 我不知道你是在學習編程的最基本概念之前寫一些控制檯遊戲的。如果你自學自我，那麼我建議你找一些像Joshua Bloch的Effective Java這樣的好書，來幫助你學習最基本和最先進的概念。

Answer 4

方法中聲明的變量（例如diceSum）僅對該特定方法是本地的。其他方法無法訪問它們。

public static void main(String[] args) { 
    int diceSum; // Can only be used in this method 
} 

public static void diceCalc() { 
    // The variable diceSum is not visible here, it can only be accessed 
    // by the main() method 
} 

但是，您可以將參數傳遞給方法。你只需將它們放在括號之間：

public static void main(String[] args) { 
    int diceSum = 3; 
    diceCalc(diceSum); 
} 

public static void diceCalc(int diceSum) { 
    // diceSum will contain the value 3 
    ... 
} 

---

這使事情變得更加動態一件好事。例如，diceCalc()方法取決於它是奇數還是偶數的菜單項號。如果您想要更改菜單項（或者創建一個圖形用戶界面，用戶單擊按鈕以選擇奇數還是偶數），則還必須更改方法diceCalc()。

Answer 5

謝謝你的幫助，但想通了。我知道我必須將我的方法更改爲int來返回參數，並且它完美地工作。

private static int diceRoll() { 
    int roll1, roll2, diceSum; 
    roll1 = (int)(Math.random()*6+1); 
    roll2 = (int)(Math.random()*6+1); 
    diceSum = roll1 + roll2; 

    System.out.println(" Dice 1 roll = " + roll1); 
    System.out.println(" Dice 2 roll = " + roll2); 
    System.out.println("TOTAL dice roll = " + diceSum); 
    return diceSum; 

} 

private static void diceCalc() { 
    if (diceSum % 2 != 0 && select == 1 || diceSum % 2 == 0 && select == 2) { 
     if (select == 1) { 
      System.out.println("\nDice rolled = " + diceSum + " and you selected odd"); 
     } else { 
      System.out.println("\nDice rolled = " + diceSum + " and you selected even"); 
     } 
     System.out.println("CONGRATULATIONS! You WIN!!"); 
     won++; 
     played++; 
    }else if (diceSum % 2 == 0 && select == 1 || diceSum % 2 != 0 && select == 2){ 
     if (select == 1) { 
      System.out.println("Dice rolled = " + diceSum + "and you selected odd"); 
     } else { 
      System.out.println("Dice rolled = " + diceSum + "and you selected even"); 
     } 
     System.out.println("I am sorry you lost!"); 
     lost++; 
     played++; 
    } 
} 

Answer 6

它在你的情況下更好地申報Dice類，然後定義你的方法是骰子

成員

還要定義select和diceSum作爲類的成員變量骰子

之後，它會是簡單的在類Dice的任何成員方法中訪問這些變量

以這種方式，您的程序將更好地組織和易於閱讀。

public class Dice { 

    private int select; 
    private int diceSum; 

    private void guess(){ 
    Scanner input = new Scanner(System.in); 
    System.out.print("(1) Odd\n" 
      +"(2) Even\n" 
      +"(3) Quit Game\n" 
      +"What is your selection: "); 

     select = input.nextInt(); 
     if(select == 1) { 
      System.out.println(""); 
      diceRoll(); 
     } else if(select == 2) { 
      System.out.println(""); 
      diceRoll(); 
     } else if(select == 3) { 
      System.out.println("Thank you for playing Dueling Dice v1.0..."); 
     } 
    } 
    private void diceRoll() { 
    int roll1, roll2; 
    roll1 = (int)(Math.random()*6+1); 
    roll2 = (int)(Math.random()*6+1); 
    diceSum = roll1 + roll2; 

    System.out.println(" Dice 1 roll = " + roll1); 
    System.out.println(" Dice 2 roll = " + roll2); 
    System.out.println("TOTAL dice roll = " + diceSum); 
    diceCalc(); // this is called in the main after the guess since guess performs the roll 
    } 

    private void diceCalc() { 
    if (diceSum % 2 != 0 && select == 1 || diceSum % 2 == 0 && select == 2) { 
     if (select == 1) { 
      System.out.println("Dice rolled = " + diceSum + "and you selected odd"); 
     } else { 
      System.out.println("Dice rolled = " + diceSum + "and you selected even"); 
     } 
     System.out.println("CONGRATULATIONS! You WIN!!"); 
     won++; 
     played++; 
    }else if (diceSum % 2 == 0 && select == 1 || diceSum % 2 != 0 && select == 2){ 
     if (select == 1) { 
      System.out.println("Dice rolled = " + diceSum + "and you selected odd"); 
     } else { 
      System.out.println("Dice rolled = " + diceSum + "and you selected even"); 
     } 
     System.out.println("I am sorry you lost!"); 
     lost++; 
     played++; 
    } 
    System.out.print("it is making it here!"); 
    } 
}