Google Guava 实战之Maps篇

 Guava是一种基于开源的Java库,谷歌很多项目使用它的很多核心库。这个库是为了方便编码,并减少编码错误。

 
     com.google.guava
     guava
     27.0.1-jre
 
 
     org.projectlombok
     lombok
 

import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.collect.*;
import lombok.AllArgsConstructor;
import lombok.Data;
import org.checkerframework.checker.nullness.qual.Nullable;


import java.util.*;

/**
 * author: lucifer
 * date: 2020/5/26 15:21
 * description: TODO
 */
public class guavaMaps01 {

    public static void main(String[] args) {

        Map map1 = new HashMap<>();
        map1.put("张三", 123);
        map1.put("李四", 457);
        map1.put("王五", 235);
        map1.put("马六", 752);
        map1.put("王八", 752);

        Map map2 = new HashMap<>();
        map2.put("张三", 345);
        map2.put("马六", 752);
        map2.put("田七", 125);

        /**
         * 1、difference
         * Maps.difference(Map, Map)用来比较两个Map以获取所有不同点。该方法返回MapDifference对象
         */
        MapDifference difference = Maps.difference(map1, map2);
        //是否有差异，返回boolean
        boolean areEqual = difference.areEqual();
        System.out.println("比较两个Map是否有差异:" + areEqual);
        //两个map的交集
        Map entriesInCommon = difference.entriesInCommon();
        System.out.println("两个map都有的部分（交集）===：" + entriesInCommon);
        //键相同但是值不同值映射项。返回的Map的值类型为MapDifference.ValueDifference，以表示左右两个不同的值
        Map> entriesDiffering = difference.entriesDiffering();
        System.out.println("键相同但是值不同值映射项===：" + entriesDiffering);
        //键只存在于左边Map的映射项
        Map onlyOnLeft = difference.entriesOnlyOnLeft();
        System.out.println("键只存在于左边Map的映射项:" + onlyOnLeft);
        //键只存在于右边Map的映射项
        Map entriesOnlyOnRight = difference.entriesOnlyOnRight();
        System.out.println("键只存在于右边Map的映射项:" + entriesOnlyOnRight);
        /**
         * 2.filterEntries
         * Maps.filterEntries():过滤map
         */
        Map filterEntries = Maps.filterEntries(map1, input -> {
            if (input.getValue().equals(123) && Objects.equals(input.getKey(), "张三")) {
                return true;
            }
            return false;
        });
        System.out.println("过滤map=====filterEntries:" + filterEntries);
        /**
         * 3.filterKeys
         * Maps.filterKeys():过滤key
         */
        Map filterKeysMap = Maps.filterKeys(map1, new Predicate() {
            @Override
            public boolean apply(@Nullable String input) {
                if (input.equals("李四")) {
                    return true;
                }
                return false;
            }
        });
        System.out.println("过滤key=====filterKeys:" + filterKeysMap);
        /**
         *4.filterValues
         * Maps.filterValues():过滤value
         */
        Map filterValuesMap = Maps.filterValues(map1, new Predicate