WannaBeFunctional

Utils.java

private static abstract class Transform1<T, M> {
    abstract M transform(T input);
}

private <InputType, OutputType, InputList extends List<InputType>, OutputList extends List<OutputType>> OutputList map (InputList input, Transform1<InputType, OutputType> transform1) {
    List<OutputType> out = new ArrayList<>();

    for (InputType i : input) {
        out.add(transform1.transform(i));
    }

    //noinspection unchecked
    return (OutputList)out;
}