How can I iterate through an ArrayList of the different class objects to search for a specific class?

productionDate is an interface that is implemented in base classes.

Here is the code but it doesn't print anything :)

ArrayList<ProductionDate> storage;

public void search(Class c, int itemCount){
   if(storage.getClass() == c){
       for(ProductionDate d : storage){
           if(d instanceof ProductionDate &&
                   ((ProductionDate)d).getItemCount() >= itemCount){
                     System.out.println(d);
           }
       }
   }
}

CodePudding user response：

First, Remove the first if statement.

Secondly, You should use the class that implements ProductionDate interface in order to check whether the object belongs to that specific class. I think that class is Class c here.

So:

ArrayList<ProductionDate> storage;

public void search(Class c, int itemCount){
    for(ProductionDate d : storage){
           if(d instanceof c &&
                   ((c)d).getItemCount() >= itemCount){
                     System.out.println(d);
           }
    }
}

CodePudding user response：

I do not know how you call the method, but this works:

import java.util.ArrayList;

public class Main {

public static void main(String[] args) {
    ArrayList<Object> arrayList = new ArrayList<>();
    Class c = arrayList.getClass();
    search(c, 12);
}

public static void search(Class c, int itemCount) {
    ArrayList<ProductionDate> storage = new ArrayList<>();
    storage.add(new ProductionDate(13));
    storage.add(new ProductionDate(15));
    storage.add(new ProductionDate(11));

    if (storage.getClass() == c) {
        for (ProductionDate d : storage) {
            if (d instanceof ProductionDate &&
                    ((ProductionDate) d).getItemCount() >= itemCount) {
                System.out.println(d);
            }
        }
    }
}


private static class ProductionDate {
    int itemCount;

    public ProductionDate(int itemCount) {
        this.itemCount = itemCount;
    }

    public int getItemCount() {
        return itemCount;
    }

}

}

output:

Main$ProductionDate@5acf9800
Main$ProductionDate@4617c264