在java中返回多个map <string，string>

Question

我试图将void方法移动到它自己的类并返回map的键值对（debitCardDetails，creditCardDetails）。什么是在父类中返回多个映射并提取的正确方法，还是我需要合并Map<String, Map<String, String>> result并返回结果？

public class CardService {

    public void serviceCall(List<CardImplementation> mapDetails) {

        final Map<String, String> debitCardDetailsMap = new HashMap<String, String>();
        final Map<String, String> creditCardDetailsMap = new HashMap<String, String>();

        /*code implementation */
        debitCardDetailsMap.put("type", "VISA");
        debitCardDetailsMap.put("bank", "BofA");
        debitCardDetailsMap.put("rank", "2");

        creditCardDetailsMap.put("type", "VISA");
        creditCardDetailsMap.put("number","23345");
        creditCardDetailsMap.put("bank", "citi");
    }
}

parentClass看起来像这样

public class ServiceClass {

CardService cardService = new CardService();
  if ( debitCardDetailsMap.size() > 0 ) {
      checkAccount(debitCardDetailsMap);
  }
  if ( creditCardDetailsMap.size()>0 ) {
     checkScore(creditCardDetailsMap);
  }
}

Answer 1

有多种方法可以实现您想要做的事情，但我建议使用OOP方式来实现。

OOP方法的优点是，代码将是模块化的，易于理解，可扩展和可扩展，而不会影响现有功能。

1. 创建一个抽象类Card，它可以是不同类型卡片的父级，即DebitCard和CreditCard
2. 创建两个java类DebitCard和CreditCard，每个类扩展Card，每个类都有自己的属性（类型，数字等），getters-setter和构造函数。
3. 有一个枚举CardType，用于定义一个字符串，用于定义卡片类型，如CREDIT_CARD，DEBIT_CARD等
4. 在serviceCall方法中，您可以使用Map<String, Map<String, String>>来保存不同类型的卡，而不是Map<CardType, List<Card>>。填充它们如下......
5. 鉴于地图中的枚举，您可以在ServiceClass中单独处理每张卡片，如下所示......

public Map<CardType, List<Card>> populateData (){
    Map<CardType, List<Card>> cardMap = new HashMap<CardType, List<Card>>();

    List<Card> debitCards = new LinkedList<Card>();
    debitCards.add(new DebitCard("Visa", "Bofa", "2"));
    cardMap.put(CardType.DEBIT_CARD, debitCards);

    List<Card> creditCards = new LinkedList<Card>();
    creditCards.add(new CreditCard("Visa", "23345", "citi"));
    cardMap.put(CardType.CREDIT_CARD, creditCards);

    return cardMap;
}

public void handleData (Map<CardType, List<Card>> cardMap) {
    if (cardMap.get(CardType.CREDIT_CARD) != 0 && cardMap.get(CardType.CREDIT_CARD).size() > 0)) {
          // do something for credit cards list
    } else if (cardMap.get(CardType.CREDIT_CARD) != 0 && cardMap.get(CardType.DEBIT_CARD).size() > 0)) {
          // do something for debit cards list
    } // have as many else as enum types
}

Answer 2

您可以返回carddetailsDTO对象并使用DTO进行游戏。像下面的东西。

mport java.util.Map;

public class CardDetailsDTO {

    private Map<String,String> debitCardDetails;

    private Map<String,String> creditCardDetails;

    public Map<String,String> getCreditCardDetails() {
        return creditCardDetails;
    }

    public void setCreditCardDetails(Map<String,String> creditCardDetails) {
        this.creditCardDetails = creditCardDetails;
    }

    public Map<String,String> getDebitCardDetails() {
        return debitCardDetails;
    }

    public void setDebitCardDetails(Map<String,String> debitCardDetails) {
        this.debitCardDetails = debitCardDetails;
    }


}

现在在主类中你可以返回此dto。

如下所示

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class CardService {

    public CardDetailsDTO serviceCall(List<?> mapDetails) {

        CardDetailsDTO cardDetailsDTO = new CardDetailsDTO();
        final Map<String, String> debitCardDetailsMap = new HashMap<String, String>();
        final Map<String, String> creditCardDetailsMap = new HashMap<String, String>();


        /*code implementation */
        debitCardDetailsMap.put("type", "VISA");
        debitCardDetailsMap.put("bank", "BofA");
        debitCardDetailsMap.put("rank", "2");

        cardDetailsDTO.setDebitCardDetails(debitCardDetailsMap);

        creditCardDetailsMap.put("type", "VISA");
        creditCardDetailsMap.put("number","23345");
        creditCardDetailsMap.put("bank", "citi");

        cardDetailsDTO.setCreditCardDetails(creditCardDetailsMap);

        return cardDetailsDTO;
    }
}

Answer 3

实际上你有很多方法可以做到，我会展示一些。

无效方法

public void populateMaps (Map<String, String> debitCardDetailsMap, Map<String, String> creditCardDetailsMap) {
    debitCardDetailsMap.put("type", "VISA");
    debitCardDetailsMap.put("bank", "BofA");
    debitCardDetailsMap.put("rank", "2");

    creditCardDetailsMap.put("type", "VISA");
    creditCardDetailsMap.put("number","23345");
    creditCardDetailsMap.put("bank", "citi");
}

你需要实例化并从调用方法传入地图，这就是你如何避免返回类型（它将保持无效）

返回Map<String, Map<String, String>>

public Map<String, Map<String, String>> populateMaps() {
    //instantiate the maps
    Map<String, Map<String, String>> map = new HashMap<>();
    final Map<String, String> debitCardDetailsMap = new HashMap<>();
    final Map<String, String> creditCardDetailsMap = new HashMap<>();

    //populate the core maps
    debitCardDetailsMap.put("type", "VISA");
    debitCardDetailsMap.put("bank", "BofA");
    debitCardDetailsMap.put("rank", "2");

    creditCardDetailsMap.put("type", "VISA");
    creditCardDetailsMap.put("number","23345");
    creditCardDetailsMap.put("bank", "citi");

    //populate the main map
    map.put(debitCardDetailsMap);
    map.put(creditCardDetailsMap);

    return map;
}

这样您就不需要在此方法之外实例化地图。

有更多方法可以创建这些地图，但我认为上面的一次展示会更好一次。