import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class ListOps {
private ListOps() {
}
public static <T> int length(final List<T> list) {
return list.size();
}
public static <T> List<T> reverse(final List<T> list) {
List<T> result = new ArrayList(list);
Collections.reverse(result);
return result;
}
public static <T> List<T> map(final List<T> list,
UnaryOperator<T> mapper) {
return list.stream().map(mapper).collect(Collectors.toList());
}
public static <T> List<T> filter(final List<T> list,
Predicate<T> predicate) {
return list.stream().filter(predicate).collect(Collectors.toList());
}
public static <U, T> U reduce(final List<T> list,
U identity,
BiFunction<U, T, U> accumulator,
BinaryOperator<U> combiner) {
return list.stream().reduce(identity, accumulator, combiner);
}
public static <T> List<T> concat(final List<T>... lists) {
return Stream.of(lists)
.flatMap(Collection::stream)
.collect(Collectors.toList());
}
}