Java 集合自定义对象属性排序

对自定义的对象属性进行排序，一般是实现Comparable接口或实现Comparator接口

1. Comparable与Comparator接口的区别

参数	Comparable	Comparator
排序逻辑	排序逻辑必须在待排序对象的类（pojo类）中	排序逻辑单独实现
实现	pojo类实现Comparable接口	自定义Comparator接口
排序方法	int compareTo(Object o1)	int compare(Object o1, Object o2)
触发排序	Collections.sort(List)	Collections.sort(List, Comparator)
接口所在包	java.lang.Comparable	java.util.Comparator

巧记两个接口：
Comparator：-tor结尾，类似doctor一样代表一个人，可以想象为是一个独立的排序接口个体，因为是个比较器个体，所以需要单独书写，单独调用；
Comparable：-able结尾，able代表xxx能力，描述自身具有的一种能力，是自身自带排序，所以不需要单独写但是要嵌入Bean中，使得Bean具有排序能力

2. 实现***Comparator***接口

package CollectionKnowledge;

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

/**
 * 集合自定义属性升序排序示例
 * @author sunlh
 *
 */
public class ComparatorSort {
	
	public static void main(String[] args) {
		List<UserBean> list = new ArrayList<>();
		UserBean user1 = new UserBean("2", "张三", "男", 23);
		UserBean user2 = new UserBean("4", "李四", "男", 24);
		UserBean user3 = new UserBean("3", "王五", "男", 25);
		UserBean user4 = new UserBean("1", "马六", "男", 26);
		list.add(user1);
		list.add(user2);
		list.add(user3);
		list.add(user4);
		System.out.println("排序前数据");
		for (UserBean userBean : list)
			System.out.println(userBean.toString());
		System.out.println("排序后数据");
		// 调用排序方法，进行排序
		ComparatorSort.sortById(list);
		for (UserBean userBean : list)
			System.out.println(userBean.toString());
	}
	
	/**
	 * 按照集合id升序排序
	 * @param list
	 */
	public static void sortById(List<UserBean> list) {
		Collections.sort(list, new Comparator<UserBean>() {
			@Override
			public int compare(UserBean u1, UserBean u2) {
				String id1 = u1.getId();
				String id2 = u2.getId();
				return id1.compareToIgnoreCase(id2);// 忽略大小写进行升序排序
			}
		});
	}
	
}

/**
 * 用户pojo
 * @author sunlh
 *
 */
class UserBean{
	private String id;
	private String name;
	private String sex;
	private int age;
	
	public UserBean(String id, String name, String sex, int age) {
		this.id = id;
		this.name = name;
		this.sex = sex;
		this.age = age;
	}
	
	public UserBean() {
		
	}
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "UserBean [id=" + id + ", name=" + name + ", sex=" + sex
				+ ", age=" + age + "]";
	}
	
}

输出结果：

排序前数据
UserBean [id=2, name=张三, sex=男, age=23]
UserBean [id=4, name=李四, sex=男, age=24]
UserBean [id=3, name=王五, sex=男, age=25]
UserBean [id=1, name=马六, sex=男, age=26]
排序后数据
UserBean [id=1, name=马六, sex=男, age=26]
UserBean [id=2, name=张三, sex=男, age=23]
UserBean [id=3, name=王五, sex=男, age=25]
UserBean [id=4, name=李四, sex=男, age=24]

---

3. 实现***Comparable***接口

package CollectionKnowledge;

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

public class ComparableSort {

	public static void main(String[] args) {
		List<UserBean2> list = new ArrayList<>();
		UserBean2 user1 = new UserBean2("2", "张三", "男", 23);
		UserBean2 user2 = new UserBean2("4", "李四", "男", 24);
		UserBean2 user3 = new UserBean2("3", "王五", "男", 25);
		UserBean2 user4 = new UserBean2("1", "马六", "男", 26);
		list.add(user1);
		list.add(user2);
		list.add(user3);
		list.add(user4);
		System.out.println("排序前数据");
		for (UserBean2 userBean2 : list)
			System.out.println(userBean2.toString());
		System.out.println("排序后数据");
		Collections.sort(list);
		for (UserBean2 userBean2 : list)
			System.out.println(userBean2.toString());
	}
}

/**
 * 用户pojo
 * @author sunlh
 *
 */
class UserBean2 implements Comparable<UserBean2>{
	private String id;
	private String name;
	private String sex;
	private int age;
	
	public UserBean2(String id, String name, String sex, int age) {
		this.id = id;
		this.name = name;
		this.sex = sex;
		this.age = age;
	}
	
	public UserBean2() {
		
	}
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "UserBean [id=" + id + ", name=" + name + ", sex=" + sex
				+ ", age=" + age + "]";
	}

	@Override
	public int compareTo(UserBean2 o) {
		return this.id.compareToIgnoreCase(o.getId());
	}
}

输出结果(同上面一样)：

排序前数据
UserBean [id=2, name=张三, sex=男, age=23]
UserBean [id=4, name=李四, sex=男, age=24]
UserBean [id=3, name=王五, sex=男, age=25]
UserBean [id=1, name=马六, sex=男, age=26]
排序后数据
UserBean [id=1, name=马六, sex=男, age=26]
UserBean [id=2, name=张三, sex=男, age=23]
UserBean [id=3, name=王五, sex=男, age=25]
UserBean [id=4, name=李四, sex=男, age=24]