如何從Java的繼承方法中調用特定的重寫方法？

Question

我有一個名為LotteryTicket的類，該類具有3個子類： Pick4 ， Pick5和Pick6 。 我希望能夠調用一個方法public void pickNumbers() ，一旦調用該方法，便能夠識別使用了哪個LotteryTicket子類，並詢問適當數量的參數（即在Pick5實例中調用pickNumbers()會詢問5個整數）。

我試圖通過在LotteryTicket類中提供4、5和6的public void pick4Numbers(int firstPick, int secondPick, int thirdPick, int fourthPick)並讓pickNumbers()方法調用適當的方法來解決此問題（ （將被覆蓋）基於字段pickAmount 。 不幸的是，這將需要提供論據。

這是LotteryTicket類：

public class LotteryTicket
{
protected int pickAmount;
protected boolean isRandom;
protected ArrayList<Integer> numbersPicked;
protected Date datePurchased;
protected SimpleDateFormat sdf;

public LotteryTicket(int pickAmount, boolean isRandom)
{
    // INITIALIZATION OF VARIABLES
    this.pickAmount = pickAmount;
    this.isRandom = isRandom;

    // CONSTRUCTION OF ARRAYLIST
    numbersPicked = new ArrayList(pickAmount);

}

/**
 * The number pick method for ALL subclasses. Running this method will run the appropriate pickxNumbers
 * method, where x is the pickAmount.
 *
 */
public void pickNumbers()
{
    if(pickAmount == 4){
        pick4Numbers(int firstPick, int secondPick, int thirdPick, int fourthPick)
    }
    if(pickAmount == 5){
        pick5Numbers(int firstPick, int secondPick, int thirdPick, int fourthPick, int fifthPick)
    }
    if(pickAmount == 6){
        pick6Numbers(int firstPick, int secondPick, int thirdPick, int fourthPick, int fifthPick, int sixthPick)
    }
}

/**
 * The number pick method for the Pick4 subclass.
 *
 */
public void pick4Numbers(int firstPick, int secondPick, int thirdPick, int fourthPick)
{

}

Pick4類：

public class Pick4 extends LotteryTicket

{

/**
 * Constructor for objects of class Pick4
 */
public Pick4(boolean isRandom)
{
    super(4, isRandom);
}

/**
 * Overloaded pick4Numbers() method. Depending on the ticket type, the amount of picks will vary.
 * For example, Pick4 tickets will only ask for 4 int values, Pick5 tickets will ask for 5, etc.
 * 
 *@param int firstPick
 *@param int secondPick
 *@param int thirdPick
 *@param int fourthPick
 */
public void pick4Numbers(int firstPick, int secondPick, int thirdPick, int fourthPick)
{
    numbersPicked.add(new Integer(firstPick));
    numbersPicked.add(new Integer(secondPick));
    numbersPicked.add(new Integer(thirdPick));
    numbersPicked.add(new Integer(fourthPick));
}

Answer 1

如果要從LotteryTicket擴展，請使pickNumbers()方法成為抽象並接受List或varargs：

public abstract class LotteryTicket {
   //...
   abstract public void pickNumbers(int... numbers);
   //...
}

然后在實現類中，例如Pick4 ：

public class Pick4 extends LotteryTicket {
   //...
   @Override
   public void pickNumbers(int... numbers) {
       if (numbers.length != 4) 
           throw IllegalArgumentException("For Pick4, there must be exactly 4 numbers!");
       for (int n : numbers) {
           numbersPicked.add(n); // no need in explicit boxing, Java will do it for you
       }
   }
}

Answer 2

我認為最好這樣做：

public class LotteryTicket {
   protected int pickAmount;
   protected boolean isRandom;
   protected List<Integer> numbersPicked;
   protected Date datePurchased;
   protected SimpleDateFormat sdf;

   protected int[] numbersToPick;

   //To create random valued ticket
   public LotteryTicket(int pickAmount) {
      this.pickAmount = pickAmount;
      isRandom = true;
   }

   //To create specified valued ticket
   public LotteryTicket(int... numbersToPick) {
      pickAmount = numbersToPick.length;
      isRandom = false;
      this.numbersToPick = numbersToPick;
   }

   public void pickNumbers() {
      numbersPicked = new ArrayList<>(pickAmount);
      if (isRandom) {
         Random random = new Random(System.currentTimeMillis());
         for (int i = 0; i < pickAmount; i++) {
            numbersPicked.add(random.nextInt());
         }
      } else {
         for (int i = 0; i < pickAmount; i++) {
            numbersPicked.add(numbersToPick[i]);
         }
      }
   }

}

而Pick4，Pick5 ...等將如下所示：

public class Pick4 extends LotteryTicket {

   //For random valued ticket  
   public Pick4() {
      super(4);
   }
   //For specified valued ticket    
   public Pick4(int pick1, int pick2, int pick3, int pick4) {
      super(pick1, pick2, pick3, pick4);
   }

}