技術標籤：Guava

場景

Multimap一個key可以對應多個value

key對應list

demo

package com.nio4444.demo;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;

import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class MultimapDemo {
    public static void main(String[] args) {
        Multimap<String,String> multimap = getMultimap();
        List<String> lowerList = (List<String>)multimap.get("lower");
        System.out.println("==" + lowerList );

        Map<String, Collection<String>> map = multimap.asMap();
        System.out.println("==map");
        for (Map.Entry<String,  Collection<String>> entry : map.entrySet()) {
            String key = entry.getKey();
            Collection<String> value =  entry.getValue();
            System.out.println(key + ":" + value);
        }

        System.out.println("==Keys:");
        Set<String> keys =  multimap.keySet();
        for(String key:keys){
            System.out.println(key);
        }

        System.out.println("==Values:");
        Collection<String> values = multimap.values();
        System.out.println(values);

    }


    private static Multimap<String,String> getMultimap(){
        Multimap<String,String> multimap = ArrayListMultimap.create();
        multimap.put("lower", "a");
        multimap.put("lower", "b");
        multimap.put("lower", "c");
        multimap.put("lower", "d");
        multimap.put("lower", "e");

        multimap.put("upper", "A");
        multimap.put("upper", "B");
        multimap.put("upper", "C");
        multimap.put("upper", "D");
        return multimap;
    }
}