<dependency> <groupId>com.github.javadev</groupId> <artifactId>underscore-java</artifactId> <version>1.14</version> </dependency> List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); List<Integer> evens = _.filter(numbers, n -> n % 2 == 0); List<Integer> squares = _.map(numbers, n -> n * n); int sum = _.reduce(numbers, (acc, n) -> acc + n, 0); Map<Boolean, List<Integer>> grouped = _.groupBy(numbers, n -> n % 2 == 0); List<Person> persons = Arrays.asList( new Person("Alice", 28), new Person("Bob", 32), new Person("Charlie", 25), new Person("David", 30) ); List<Person> filtered = _.filter(persons, p -> p.getAge() > 30); List<String> names = _.map(persons, Person::getName); Map<Integer, List<Person>> grouped = _.groupBy(persons, Person::getAge); List<Person> merged = _.concat(persons, filtered); List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); List<Integer> result = _.chain(numbers) .filter(n -> n % 2 == 0) .map(n -> n * n) .value(); List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); int sum = _.stream(numbers) .filter(n -> n % 2 == 0) .mapToInt(n -> n) .sum();