HashMap、LinkedHashMap、TreeMap

1. hashMap

 

 

 

 

 

 

2. LinkedHashMap

 

 上一个会记住下一个的地址

 

 

 

3. TreeMap

 

 

例：

import d3_genericity.set.Apple;

import java.util.Comparator;
import java.util.Map;
import java.util.TreeMap;

public class TreeMapDemo {
    public static void main(String[] args) {
        Map<Integer, String> maps1 = new TreeMap<>();

        maps1.put(22, "wl");
        maps1.put(23, "phx");
        maps1.put(2, "lr");
        System.out.println(maps1);

        // TreeMap自带排序
        Map<Apple, String> maps2 = new TreeMap<>(new Comparator<Apple>() {
            @Override
            public int compare(Apple o1, Apple o2) {
                // 降序， 因为价钱没有相等的，所以不会覆盖
                return Double.compare(o2.getPrice(), o1.getPrice());
            }
        });
        maps2.put(new Apple("红富士", "红色", 15.2, 500), "上海");
        maps2.put(new Apple("青苹果", "绿色", 9.9, 600), "重庆");
        maps2.put(new Apple("白苹果", "白色", 8.8, 600), "四川");

        System.out.println(maps2);
    }
}