在Java中在一个单例类中缓存数据并在另一个单例类中使用

Question

我有一个类，它调用两个单例类FirstClass和SecondClass，如下所示。有没有一种方法可以在第二类中访问第一类中计算的数据。在这种情况下，我不想在第二类中进行外部服务调用，因为第一类已经调用了它。相反，只需在第二个数据函数中使用数据（存储在第一类函数中）。有什么方法可以做到。

public class CallingFunction() {
    List<String> generateData() {
    return Lists.newArrayList(new FirstClass(), new SecondClass())
}

@Singleton
public class FirstClass() extends interface {
    public String function() { 
    //operations. This function calls multiple services and stores ouput  to hashMap
    Map<String, String> hashedData = Maps.newHashMap();
    hashedData.put(dataFromAnotherService);
    return hashedData.get("abc");
    }
}

@Singleton
public class SecondClass() extends interface {
    public String function() { 
    //Use hashedData here instead of invoking the service again.
    //Other operations
    return "data";
    }
}

Answer 1

是的，您可以通过以下逻辑来实现功能：

@Singleton
public class FirstClass() extends interface {
    private static FirstClass instance;
    private Map<String, String> hashedData = new HashMap<>();
    public String function() { 
        //operations. This function calls multiple services and stores ouput  to hashMap

        hashedData.put(dataFromAnotherService);
        return hashedData.get("abc");
    }
    public Map<String, String> getHashedData() {
        return this.hashedData;
    }
    public static FirstClass getInstance() {
         if (instance == null) instance = new FirstClass();
         return instance;
    }
}

@Singleton
public class SecondClass() extends interface {
    public String function() { 
         FirstClass instance = FirstClass.getInstance();

         // instance.getHashedData() here instead of invoking the service again.
         //Other operations
         return "data";
    }
}