Java中List对象集合按照对象中某字段进行排序

在Java中,可以使用List集合对象的sort(Comparator c)方法，按照对象中某字段对List集合进行排序

default void sort(Comparator<? super E> c) {
    Object[] a = this.toArray();
    Arrays.sort(a, (Comparator) c);
    ListIterator<E> i = this.listIterator();
    for (Object e : a) {
        i.next();
        i.set((E) e);
    }
}

栗子:

import java.util.*;
import java.util.stream.Collectors;

public class StreamTest {
    public static void main(String[] args) {

        List<Person2> personList = new ArrayList<Person2>();
        personList.add(new Person2("Tom", 8900, 18,"male", "A"));
        personList.add(new Person2("Jack", 7000, 19,"male", "A"));
        personList.add(new Person2("Lily", 7800, 20,"female", "D"));
        personList.add(new Person2("Anni", 8200, 18,"female", "B"));
        personList.add(new Person2("Owen", 9500, 23,"male", "D"));
        personList.add(new Person2("Alisa", 7900, 28,"female", "C"));
  
        //根据List集合对象的sort方法(语句后x.get与y.get调换位置即为倒序)
        personList.sort((x,y) -> Integer.compare(x.getSalary(),y.getSalary()));//int类型正序
        personList.forEach(System.out::println);
        System.out.println("================================");

        personList.sort((a, b) -> a.getSalary() - b.getSalary());//int类型正序
        personList.forEach(System.out::println);
        System.out.println("================================");

        personList.sort(Comparator.comparing(Person2::getSalary));//int类型正序排序
        personList.forEach(System.out::println);
        System.out.println("================================");

        personList.sort((a,b) -> a.getLevel().compareTo(b.getLevel()));//其他类型正序
        personList.forEach(System.out::println);
        System.out.println("================================");

        //stream流的sorted方法正序排序(倒序：Comparator.comparing(Person2::getSalary).reversed())
        personList = personList.stream().sorted(Comparator.comparing(Person2::getSalary)).collect(Collectors.toList());
        personList.forEach(System.out::println);
        System.out.println("================================");
    }
}


class Person2 {
    private String name;  // 姓名
    private int salary; // 薪资
    private int age; // 年龄
    private String sex; //性别
    private String level;  // 级别

    // 构造方法
    public Person2(String name, int salary, int age, String sex, String level) {
        this.name = name;
        this.salary = salary;
        this.age = age;
        this.sex = sex;
        this.level = level;
    }
    // 省略了get和set，请自行添加

    public String getName() {
        return name;
    }

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

    public int getSalary() {
        return salary;
    }

    public void setSalary(int salary) {
        this.salary = salary;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getLevel() {
        return level;
    }

    public void setLevel(String level) {
        this.level = level;
    }

    @Override
    public String toString() {
        return "Person2{" +
                "name=" + name +
                ", salary='" + salary + '\'' +
                ", age='" + age + '\'' +
                ", sex='" + sex + '\'' +
                ", level=" + level +
                '}';
    }
}

打印输出结果如下:

Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================
Person2{name=Jack, salary='7000', age='19', sex='male', level=A}
Person2{name=Lily, salary='7800', age='20', sex='female', level=D}
Person2{name=Alisa, salary='7900', age='28', sex='female', level=C}
Person2{name=Anni, salary='8200', age='18', sex='female', level=B}
Person2{name=Tom, salary='8900', age='18', sex='male', level=A}
Person2{name=Owen, salary='9500', age='23', sex='male', level=D}
================================