对于那些能够使用Java 8流API的人来说，这里有一个更整洁的方法: lambda和排序

我正在寻找相当于c# LINQ:

.ThenBy(...)

我在Comparator上找到了Java 8的机制:

.thenComparing(...)

下面是演示算法的代码片段。

    Comparator<Person> comparator = Comparator.comparing(person -> person.name);
    comparator = comparator.thenComparing(Comparator.comparing(person -> person.age));

请查看上面的链接，以获得更简洁的方法，并解释Java的类型推断如何使其与LINQ相比定义起来更笨拙。

下面是完整的单元测试供参考:

@Test
public void testChainedSorting()
{
    // Create the collection of people:
    ArrayList<Person> people = new ArrayList<>();
    people.add(new Person("Dan", 4));
    people.add(new Person("Andi", 2));
    people.add(new Person("Bob", 42));
    people.add(new Person("Debby", 3));
    people.add(new Person("Bob", 72));
    people.add(new Person("Barry", 20));
    people.add(new Person("Cathy", 40));
    people.add(new Person("Bob", 40));
    people.add(new Person("Barry", 50));

    // Define chained comparators:
    // Great article explaining this and how to make it even neater:
    // http://blog.jooq.org/2014/01/31/java-8-friday-goodies-lambdas-and-sorting/
    Comparator<Person> comparator = Comparator.comparing(person -> person.name);
    comparator = comparator.thenComparing(Comparator.comparing(person -> person.age));

    // Sort the stream:
    Stream<Person> personStream = people.stream().sorted(comparator);

    // Make sure that the output is as expected:
    List<Person> sortedPeople = personStream.collect(Collectors.toList());
    Assert.assertEquals("Andi",  sortedPeople.get(0).name); Assert.assertEquals(2,  sortedPeople.get(0).age);
    Assert.assertEquals("Barry", sortedPeople.get(1).name); Assert.assertEquals(20, sortedPeople.get(1).age);
    Assert.assertEquals("Barry", sortedPeople.get(2).name); Assert.assertEquals(50, sortedPeople.get(2).age);
    Assert.assertEquals("Bob",   sortedPeople.get(3).name); Assert.assertEquals(40, sortedPeople.get(3).age);
    Assert.assertEquals("Bob",   sortedPeople.get(4).name); Assert.assertEquals(42, sortedPeople.get(4).age);
    Assert.assertEquals("Bob",   sortedPeople.get(5).name); Assert.assertEquals(72, sortedPeople.get(5).age);
    Assert.assertEquals("Cathy", sortedPeople.get(6).name); Assert.assertEquals(40, sortedPeople.get(6).age);
    Assert.assertEquals("Dan",   sortedPeople.get(7).name); Assert.assertEquals(4,  sortedPeople.get(7).age);
    Assert.assertEquals("Debby", sortedPeople.get(8).name); Assert.assertEquals(3,  sortedPeople.get(8).age);
    // Andi     : 2
    // Barry    : 20
    // Barry    : 50
    // Bob      : 40
    // Bob      : 42
    // Bob      : 72
    // Cathy    : 40
    // Dan      : 4
    // Debby    : 3
}

/**
 * A person in our system.
 */
public static class Person
{
    /**
     * Creates a new person.
     * @param name The name of the person.
     * @param age The age of the person.
     */
    public Person(String name, int age)
    {
        this.age = age;
        this.name = name;
    }

    /**
     * The name of the person.
     */
    public String name;

    /**
     * The age of the person.
     */
    public int age;

    @Override
    public String toString()
    {
        if (name == null) return super.toString();
        else return String.format("%s : %d", this.name, this.age);
    }
}

对于像这样的一本书:

package books;

public class Book {

    private Integer id;
    private Integer number;
    private String name;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getNumber() {
        return number;
    }

    public void setNumber(Integer number) {
        this.number = number;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "book{" +
                "id=" + id +
                ", number=" + number +
                ", name='" + name + '\'' + '\n' +
                '}';
    }
}

用模拟对象对主类进行排序

package books;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;


public class Main {

    public static void main(String[] args) {
        System.out.println("Hello World!");

        Book b = new Book();

        Book c = new Book();

        Book d = new Book();

        Book e = new Book();

        Book f = new Book();

        Book g = new Book();
        Book g1 = new Book();
        Book g2 = new Book();
        Book g3 = new Book();
        Book g4 = new Book();




        b.setId(1);
        b.setNumber(12);
        b.setName("gk");

        c.setId(2);
        c.setNumber(12);
        c.setName("gk");

        d.setId(2);
        d.setNumber(13);
        d.setName("maths");

        e.setId(3);
        e.setNumber(3);
        e.setName("geometry");

        f.setId(3);
        f.setNumber(34);
        b.setName("gk");

        g.setId(3);
        g.setNumber(11);
        g.setName("gk");

        g1.setId(3);
        g1.setNumber(88);
        g1.setName("gk");
        g2.setId(3);
        g2.setNumber(91);
        g2.setName("gk");
        g3.setId(3);
        g3.setNumber(101);
        g3.setName("gk");
        g4.setId(3);
        g4.setNumber(4);
        g4.setName("gk");





        List<Book> allBooks = new ArrayList<Book>();

        allBooks.add(b);
        allBooks.add(c);
        allBooks.add(d);
        allBooks.add(e);
        allBooks.add(f);
        allBooks.add(g);
        allBooks.add(g1);
        allBooks.add(g2);
        allBooks.add(g3);
        allBooks.add(g4);



        System.out.println(allBooks.size());


        Collections.sort(allBooks, new Comparator<Book>() {

            @Override
            public int compare(Book t, Book t1) {
                int a =  t.getId()- t1.getId();

                if(a == 0){
                    int a1 = t.getNumber() - t1.getNumber();
                    return a1;
                }
                else
                    return a;
            }
        });
        System.out.println(allBooks);

    }


   }

你可以这样做:

List<User> users = Lists.newArrayList(
  new User("Pedro", 12), 
  new User("Maria", 10), 
  new User("Rafael",12)
);

users.sort(
  Comparator.comparing(User::getName).thenComparing(User::getAge)
);

您可以使用集合。排序如下:

private static void order(List<Person> persons) {

    Collections.sort(persons, new Comparator() {

        public int compare(Object o1, Object o2) {

            String x1 = ((Person) o1).getName();
            String x2 = ((Person) o2).getName();
            int sComp = x1.compareTo(x2);

            if (sComp != 0) {
               return sComp;
            } 

            Integer x1 = ((Person) o1).getAge();
            Integer x2 = ((Person) o2).getAge();
            return x1.compareTo(x2);
    }});
}

List<Persons>现在按姓名排序，然后按年龄排序。

compareto "按字典顺序比较两个字符串" -来自文档。

集合。sort是本地Collections库中的一个静态方法。它做实际的排序，你只需要提供一个Comparator来定义如何比较列表中的两个元素:这是通过提供你自己的compare方法实现来实现的。

我不确定在Person类中写比较器是否丑陋。是这样的:

public class Person implements Comparable <Person> {

    private String lastName;
    private String firstName;
    private int age;

    public Person(String firstName, String lastName, int BirthDay) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = BirthDay;
    }

    public int getAge() {
        return age;
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }

    @Override
    public int compareTo(Person o) {
        // default compareTo
    }

    @Override
    public String toString() {
        return firstName + " " + lastName + " " + age + "";
    }

    public static class firstNameComperator implements Comparator<Person> {
        @Override
        public int compare(Person o1, Person o2) {
            return o1.firstName.compareTo(o2.firstName);
        }
    }

    public static class lastNameComperator implements Comparator<Person> {
        @Override
        public int compare(Person o1, Person o2) {
            return o1.lastName.compareTo(o2.lastName);
        }
    }

    public static class ageComperator implements Comparator<Person> {
        @Override
        public int compare(Person o1, Person o2) {
            return o1.age - o2.age;
        }
    }
}
public class Test {
    private static void print() {
       ArrayList<Person> list = new ArrayList();
        list.add(new Person("Diana", "Agron", 31));
        list.add(new Person("Kay", "Panabaker", 27));
        list.add(new Person("Lucy", "Hale", 28));
        list.add(new Person("Ashley", "Benson", 28));
        list.add(new Person("Megan", "Park", 31));
        list.add(new Person("Lucas", "Till", 27));
        list.add(new Person("Nicholas", "Hoult", 28));
        list.add(new Person("Aly", "Michalka", 28));
        list.add(new Person("Adam", "Brody", 38));
        list.add(new Person("Chris", "Pine", 37));
        Collections.sort(list, new Person.lastNameComperator());
        Iterator<Person> it = list.iterator();
        while(it.hasNext()) 
            System.out.println(it.next().toString()); 
     }  
}    

让你的person类实现Comparable< person >，然后实现compareTo方法，例如:

public int compareTo(Person o) {
    int result = name.compareToIgnoreCase(o.name);
    if(result==0) {
        return Integer.valueOf(age).compareTo(o.age);
    }
    else {
        return result;
    }
}

它将首先按名称(大小写不敏感)排序，然后按年龄排序。然后可以在Person对象的集合或数组上运行Arrays.sort()或Collections.sort()。