map排序

1.

public class DemoTreeMap3 {
    public static void main(String[] args) {
        System.out.println("------对hashMap按照key进行排序----------");
        Map<Car,String> map   = new HashMap<Car,String>();
        map.put(new Car("凯迪拉克",50),"看iadilake1");
        map.put(new Car("法拉利",100),"阿迪发送发的");
        map.put(new Car("大众", 20), "迈腾");
        
        Comparator<Car> c = new CarComparator();
        Map<Car,String> map2   = new TreeMap<Car,String>(c);
        map2.putAll(map);
        
        Set<Car> set = map2.keySet();
        for (Car car : set) {
            System.out.println(car.getPrice()+"--"+car.getType());
        }
        
        System.out.println("------对hashMap按照value进行排序----------");
        //对HashMap按照value进行排序
        Map<String,Car> map3   = new HashMap<String,Car>();
        map3.put("大众",new Car("凯迪拉克",50));
        map3.put("法拉利",new Car("法拉利",100));
        map3.put("福特",new Car("福特", 20));
        
        
        //第一步：把待排序map集合的引用传递进入自定义比较器
        //第二步：在自定义比较器中，加入成员变量，接收map集合的引用
        Comparator<String> compar = new CarComparator2(map3);
        Map<String,Car> treeMap = new TreeMap<String,Car>(compar);
        treeMap.putAll(map3);
        
        Collection<Car> cars = treeMap.values();
        for (Car car : cars) {
            System.out.println(car.getPrice()+"--"+car.getType());
        }
        
    }

}

import java.util.Comparator;

public class CarComparator implements Comparator<Car>{

    @Override
    public int compare(Car o1, Car o2) {
        return (int)(o1.getPrice()-o2.getPrice());
    }

}

public class CarComparator2 implements Comparator<String> {

    private Map<String, Car> map;

    public CarComparator2(Map<String, Car> map3) {
        this.map = map3;
    }

    @Override
    public int compare(String key1, String key2) {
        Car car1 = map.get(key1);
        Car car2 = map.get(key2);

        return (int) (car1.getPrice() - car2.getPrice());
    }

}