Java: Converting lists of one element type to a list of another type

Question

I\'m writing an adapter framework where I need to convert a list of objects from one class to another. I can iterate through the source list to do this as in

Java: Best

Answer 1

As an alternative to the iterator pattern, you can use a abstract generic mapper class, and only override the transform method:

1. create a generic collection mapper for any data type
2. [optional] create a library of methods that transform between different data types (and override the method)
3. use that library

the implementation:

// Generic class to transform collections
public abstract class CollectionTransformer {

    abstract F transform(E e);

    public List transform(List list) {
        List newList = new ArrayList();
        for (E e : list) {
            newList.add(transform(e));
        }
        return newList;
    }
}

// Method that transform Integer to String
// this override the transform method to specify the transformation
public static List mapIntegerToStringCollection(List list) {

    CollectionTransformer transformer = new CollectionTransformer() {
        @Override  
        String transform(Integer e) {
            return e.toString();
        }
    };
    return transformer.transform(list);
}

// Example Usage
List integers = Arrays.asList(1,2);
List strings = mapIntegerToStringCollection(integers);

This would be useful is you have to use transformations every time, encapsulating the process. So you can make a library of collection mappers very easy.