Comparator，Collections对List排序！_collections max comparator-优快云博客

本文介绍了一种在Java中实现自定义比较器的方法，并通过示例展示了如何使用该比较器对包含金钱属性的Person对象列表进行排序。此外，还介绍了如何查找列表中的最小元素。

package cn.vicky.vo; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; public class Person implements Comparator<Person> { private int id = 0; private String username = ""; private String password = ""; private double money = 0.0; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public double getMoney() { return money; } public void setMoney(double money) { this.money = money; } public int compare(Person p1, Person p2) { if (p1 == null || p2 == null) { return -2; } if (p1.getMoney() > p2.getMoney()) { return 1; } else if (p1.getMoney() < p2.getMoney()) { return -1; } return 0; } public static void main(String[] args) { Person p1 = new Person(); p1.setMoney(10.0); Person p2 = new Person(); p2.setMoney(8.0); Person p3 = new Person(); p3.setMoney(9.0); Person p4 = new Person(); p4.setMoney(11.0); System.out.println(p1.compare(p1, p2)); System.out.println(p1.compare(p2, p1)); System.out.println(p1.compare(null, null)); System.out.println("-------------"); List<Person> persons = new ArrayList<Person>(); persons.add(p1); persons.add(p2); persons.add(p3); persons.add(p4); for (Person p : persons) { System.out.println(p.getMoney()); } System.out.println("-------------"); Collections.sort(persons, p1); for (Person p : persons) { System.out.println(p.getMoney()); } System.out.println("-------------"); Person minP = Collections.min(persons, new Person()); System.out.println(minP.getMoney()); } }

打印：

1
-1
-2
-------------
10.0
8.0
9.0
11.0
-------------
8.0
9.0
10.0
11.0
-------------
8.0

package cn.vicky.vo; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; public class MyComparator implements Comparator<Person2> { public int compare(Person2 o1, Person2 o2) { if (o1.getMoney() > o2.getMoney()) { return 1; } else if (o1.getMoney() < o2.getMoney()) { return -1; } return 0; } public static void main(String[] args) { Person2 p1 = new Person2(); p1.setMoney(10.1); Person2 p2 = new Person2(); p2.setMoney(0.1); Person2 p3 = new Person2(); p3.setMoney(5.1); Person2 p4 = new Person2(); p4.setMoney(2); Person2 p5 = new Person2(); p5.setMoney(5); MyComparator myComparator = new MyComparator(); myComparator.compare(p1, p2); List<Person2> persons = new ArrayList<Person2>(); persons.add(p1); persons.add(p2); persons.add(p3); persons.add(p4); persons.add(p5); for (Person2 p : persons) { System.out.println(p.getMoney()); } System.out.println("------------"); Collections.sort(persons, new MyComparator()); for (Person2 p : persons) { System.out.println(p.getMoney()); } System.out.println("------------"); Collections.sort(persons, new MyComparator()); for (Person2 p : persons) { System.out.println(p.getMoney()); } System.out.println("------------"); Person2 p = Collections.max(persons,new MyComparator()); System.out.println(p.getMoney()); } }

打印：

10.1
0.1
5.1
2.0
5.0
------------
0.1
2.0
5.0
5.1
10.1
------------
0.1
2.0
5.0
5.1
10.1
------------
10.1