Convert a generic list to an array

Question

I have searched for this, but unfortunately, I don\'t get the correct answer.

class Helper {
    public static  T[] toArray(List list) {
           


        

Answer 1

Worked solution!

Just copy interface and class inside your project. This :

public interface LayerDataTransformer {
    T transform(F from);

    Collection transform(Collection from);

    T[] toArray(Collection from);
}

and this :

public abstract class BaseDataLayerTransformer implements LayerDataTransformer {

    @Override
    public List transform(Collection from) {
        List transformed = new ArrayList<>(from.size());

        for (F fromObject : from) {
            transformed.add(transform(fromObject));
        }

        return transformed;
    }

    @Override
    public T[] toArray(Collection from) {
        Class clazz = (Class) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[1];
        T[] transformedArray = (T[]) java.lang.reflect.Array.newInstance(clazz, from.size());

        int index = 0;
        for (F fromObject : from) {
            transformedArray[index] = transform(fromObject);
            index++;
        }

        return transformedArray;
    }
}

Usage.

Declare a subclass of BaseDataLayerTransformer

public class FileToStringTransformer extends BaseDataLayerTransformer {
    @Override
    public String transform(File file) {
        return file.getAbsolutePath();
    }
}

And use :

FileToStringTransformer transformer = new FileToStringTransformer();
List files = getFilesStub();// returns List
//profit!
String[] filePathArray = transformer.toArray(files);