I want to create a very generic utility method to take any Collection and convert it into a Collection of a user selectable class that extends from Number (Long, Double, Float, Integer, etc.)
I came up with this code that uses Google Collections to transform the Collection and to return an Immutable List.
import java.util.List;
import com.google.common.base.Function;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
/**
* Takes a {@code List<String>} and transforms it into a list of the
* specified {@code clazz}.
*
* @param <T>
* @param stringValues
* the list of Strings to be used to create the list of the
* specified type
* @param clazz
* must be a subclass of Number. Defines the type of the new List
* @return
*/
public static <T extends Number> List<T> toNumberList(List<String> stringValues, final Class<T> clazz) {
List<T> ids = Lists.transform(stringValues, new Function<String, T>() {
@SuppressWarnings("unchecked")
@Override
public T apply(String from) {
T retVal = null;
if (clazz.equals(Integer.class)) {
retVal = (T) Integer.valueOf(from);
} else if (clazz.equals(Long.class)) {
retVal = (T) Long.valueOf(from);
} else if (clazz.equals(Float.class)) {
retVal = (T) Float.valueOf(from);
} else if (clazz.equals(Double.class)) {
retVal = (T) Double.valueOf(from);
} else {
throw new RuntimeException(String.format("Type %s is not supported (yet)", clazz.getName()));
}
return retVal;
}
});
return ImmutableList.copyOf(ids);
}
It can be used like this:
// Convert List<String> to List<Long>
List<Long> ids = MiscUtils.toNumberList(productIds, Long.class);
Is my code overkill or how would you simplify it and at the same time keep it generic enough?