泛型的排序问题（Collections.sort及Comparable的应用）

喜欢ヅ旅行 2022-06-05 08:27 162阅读 0赞

参考博文： [http://www.cnblogs.com/hongwz/p/5887899.html][http_www.cnblogs.com_hongwz_p_5887899.html]

**一.前言**

**  **  java中对泛型(集合类型)排序的问题，主要采用了两张方式一种是对要排序的实体类，实现Comparable接口，另一种方式，Collections集合工具类进行排序。

**二.实现Comparable接口方式**

package com.shine.demo.test;
    
    import java.io.Serializable;
    
    public class Car implements Serializable, Comparable<Car> {
        
        /**
         * 序列化版本.
         */
        private static final long serialVersionUID = 5854674665110917200L;
    
        private Long id;
        
        private String name;
    
        public Long getId() {
            return id;
        }
    
        public void setId(Long id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        @Override
        public int compareTo(Car car) {
            if(!this.id.equals(car.getId()))
                return this.id.compareTo(car.getId());
            else if(!this.name.equals(car.getName()))
                return this.name.compareTo(car.getName());
            
            return 0;
        }
        
        @Override
        public String toString() {
            return "Car的id为：" + this.id + ",名称为：" + this.name;
        }
        
    }

实现了Comparable接口，重写compareTo方法。

**三.Collections集合工具**

package com.shine.demo.test;
    
    import java.util.ArrayList;
    import java.util.Collections;
    import java.util.Comparator;
    import java.util.List;
    import java.util.Set;
    import java.util.TreeSet;
    
    public class Test {
        
        public static void main(String[] args) {
            
            Car car = new Car();
            car.setId(1L);
            car.setName("小汽车");
            
            Car car1 = new Car();
            car1.setId(2L);
            car1.setName("货车");
            
            Car car2 = new Car();
            car2.setId(3L);
            car2.setName("载客小汽车");
            
            Car car3 = new Car();
            car3.setId(4L);
            car3.setName("出租车");
            
            //使用Comparable与Set进行排序
            Set<Car> cars = new TreeSet<Car>();
            cars.add(car);
            cars.add(car3);
            cars.add(car1);
            cars.add(car2); 
            
            for (Car carInfo : cars) {
                System.out.println(carInfo);
            }
            
            //常用Collections的sort排序
            List<Car> carList = new ArrayList<Car>();
            carList.add(car);
            carList.add(car3);
            carList.add(car1);
            carList.add(car2); 
            
            Collections.sort(carList, new Comparator<Car>() {
                
                @Override
                public int compare(Car car1, Car car2) {
                    return (int) (car1.getId() - car2.getId());
                }
            });
            
            for (Car carInfoList : carList) {
                System.out.println(carInfoList);
            }
            
            
        }
    
    }

采用了Collections的sort排序方法，其原理是利用了Comparator的类，进行排序。

[http_www.cnblogs.com_hongwz_p_5887899.html]: http://www.cnblogs.com/hongwz/p/5887899.html