Java 8のStream APIでソートを実装する

Library.java

import java.util.List;
import java.util.stream.Collectors;

import static java.util.Comparator.comparing;

public class Library {
    public List<Model> sortWithName(List<Model> models) {
        return models.stream() // このmodelsの中身は変更されない
                .sorted(comparing(model -> model.name))　// 適当に降順ソート
                .collect(Collectors.toList()); // このときに新しいList<Model>型コレクションが生成される
    }
}

LibraryTest.groovy

import spock.lang.Specification

class LibraryTest extends Specification {
    def "sortWithName success"() {
        setup:
        def lib = new Library()
        def models = [
                new Model(24, "Nougat"),
                new Model(11, "Honeycomb"),
                new Model(8, "Eclair"),
                new Model(19, "KitKat"),
                new Model(4, "Cupcake"),
        ]

        when:
        def result = lib.sortWithName(models)

        then:
        result == [
                new Model(4, "Cupcake"),
                new Model(8, "Eclair"),
                new Model(11, "Honeycomb"),
                new Model(19, "KitKat"),
                new Model(24, "Nougat"),
        ]
    }
}

Model.java

import java.util.Objects;

public class Model {
    public final int id;
    public final String name;

    public Model(int id, String name) {
        this.id = id;
        this.name = name;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Model model = (Model) o;
        return id == model.id &&
                Objects.equals(name, model.name);
    }

    @Override
    public int hashCode() {

        return Objects.hash(id, name);
    }
}