从数组中删除对象与多个类在Java

Question

我对Java相当陌生，在这个练习中我遇到了一些困难。我必须创建一个“Piggy Bank”，用户可以在其中存入不同价值和货币（欧元、多拉、雷亚尔等）的硬币，并在之后将其移除，然后将总价值转换为所需的货币。建议我们为Coin创建一个抽象超类，为Euro、Dolar和Real创建三个子类。我可以在没有外壳的情况下走得很远，但我不知道如何移除，例如，银行中的任何10美元硬币，而让其他10美元或10欧元硬币保持不变，就像一个扫描数组的Iterator，当他满足条件（dollar，value 10）时，他移除该对象并停止运行。我正在创建一个数组列表，并通过以下代码块在其上放置硬币：

ArrayList<Coin> list = new ArrayList<Coin>();

double euroCoinValue = scan.nextDouble();
list.add(new Euro(euroCoinValue)); 

double dollarCoinValue = scan.nextDouble();
list.add(new Dollar(dollarCoinValue)); 

Answer 1

这是我对你想做什么的理解。如果我错过了你的实际问题，请告诉我。

import java.math.BigDecimal;
import java.util.List;
import java.util.ArrayList;
import java.util.stream.Collectors;

public class Main {
  public static void main(String[] args) {
    Main main = new Main();
    main.testRemoveOneOfTheDollars();

    main.testRemoveOneReal();

    main.testRemoveTwoReal();

  }

  private PiggyBank setup() {
    PiggyBank piggyBank = new PiggyBank();
    piggyBank.add(new Euro(BigDecimal.valueOf(10L)));
    piggyBank.add(new Dollar(BigDecimal.valueOf(10L)));
    piggyBank.add(new Euro(BigDecimal.valueOf(10L)));
    piggyBank.add(new Dollar(BigDecimal.valueOf(10L)));
    piggyBank.add(new Real(BigDecimal.valueOf(10L)));
    return piggyBank;

  }

  public void testRemoveOneOfTheDollars() {
    PiggyBank piggyBank = setup();
    piggyBank.printCurrentState();
    piggyBank.remove("Main$Dollar");

  }

  public void testRemoveOneReal() {
    PiggyBank piggyBank = setup();
    piggyBank.printCurrentState();
    piggyBank.remove("Main$Real");
    piggyBank.printCurrentState();
  }

  public void testRemoveTwoReal() {
    PiggyBank piggyBank = setup();
    piggyBank.printCurrentState();
    piggyBank.remove("Main$Real");
    piggyBank.printCurrentState();
    try {
      piggyBank.remove("Main$Real");
    } catch (IllegalStateException e) {
      System.out.println(e.getMessage());
    }
    piggyBank.printCurrentState();
  }

  class PiggyBank {
    private List<Coin> coins;

    public PiggyBank() {
      coins = new ArrayList<Coin>();
    }

    public void add(Coin newCoin) {
      System.out.println("Adding coin [" + newCoin + "]");
      coins.add(newCoin);
    }

    public Coin remove(String coinType) {
      System.out.println("Removing coin of type [" + coinType + "]");
      int numOfCoins = coins.size();
      for (int i = 0; i < numOfCoins; i++) {
        Coin toReturn = coins.get(i);
        if (toReturn.getClass().getName().equalsIgnoreCase(coinType)) {
          coins.remove(i);
          System.out.println("Removed coin [" + toReturn + "]");
          return toReturn;
        }
      }
      throw new IllegalStateException("No Coins of type [" + coinType + "] exist in PiggyBank");
    }

    public void printCurrentState() {
      List<String> coinStrs = coins.stream().map(Coin::toString).collect(Collectors.toList());
      System.out.println("PiggyBank Current State [" + coinStrs + "]");

    }

  }

  abstract class Coin {
    protected BigDecimal value;

    public Coin(BigDecimal value) {
      this.value = value;
    }

    public BigDecimal getValue() {
      return value;
    }

    public String toString() {
      return "value: [" + getValue() + "], type [" + this.getClass().getName() + "]\n";
    }

  }

  class Euro extends Coin {
    public Euro(BigDecimal value) {
      super(value);
    }
  }

  class Dollar extends Coin {
    public Dollar(BigDecimal value) {
      super(value);
    }
  }

  class Real extends Coin {
    public Real(BigDecimal value) {
      super(value);
    }
  }

}