Guava（四）：集合基础总结之Map-蒲公英云

其实Guavad的集合操作适合我们平时使用的原生的集合是一样的，只是他将我们平时操作的集合更加的流畅优雅加单。其实Map就和List一样也是在创建的时候和其他的一些很赞的方法，但是呢好像这些方法我们平时的工作中用到的很少，但是呢我们还是来看看把。

首先说一下这几个方法：

1：创建Map方法：

Map<String,String> guavaMap = Maps.newHashMap();

2：集合diff方法：两个Map中都有的映射项，包括匹配的键与值

MapDifference<String,String> diffMap = Maps.difference(map,guavaMap);

3：也是集合方法：键只存在于左边Map的映射项，也就是说左边参数map里面有的而右边没有的就展示：

entriesOnlyOnLeft()

4：也是集合方法：键只存在于右边Map的映射项

entriesOnlyOnRight()

好了上代码：

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.MapDifference;
import com.google.common.collect.Maps;
import java.util.HashMap;
import java.util.Map;
/**
 * Created by luyangli on 15-9-19.
 */
public class MapsTest {
    public static void main(String[] args) {
        Map<String,String> map = new HashMap<String, String>();
        map.put("3","c");
        map.put("1","a");
        map.put("2","b");
        map.put("4","t");
        System.out.println("========原生Map=======");
        for (Map.Entry<String, String> entry : map.entrySet()) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
        Map<String,String> guavaMap = Maps.newHashMap();
        guavaMap.put("3","c");
        guavaMap.put("1","a");
        guavaMap.put("2","b");
        guavaMap.put("5","t");
        System.out.println("========Guava Map=======");
        for (Map.Entry<String, String> entry : guavaMap.entrySet()) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
        MapDifference<String,String> diffMap = Maps.difference(map,guavaMap);
        System.out.println("========Guava diff Map=======");
        for (Map.Entry<String, String> entry : diffMap.entriesInCommon().entrySet()) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
        System.out.println("========Guava diff Left Map=======");
        for (Map.Entry<String, String> entry : diffMap.entriesOnlyOnLeft().entrySet()) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
        System.out.println("========Guava diff Right Map=======");
        for (Map.Entry<String, String> entry : diffMap.entriesOnlyOnRight().entrySet()) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
//        Map<String, Integer> left = ImmutableMap.of("a", 1, "b", 2, "c", 3);
//        Map<String, Integer> right = ImmutableMap.of("a", 1, "b", 2, "c", 3);
//        MapDifference<String, Integer> diff = Maps.difference(left, right);
//        Map<String,Integer> map2 = diff.entriesInCommon();
//        System.out.println("========Guava diff Map=======");
//        for (Map.Entry<String, Integer> entry : map2.entrySet()) {
//            System.out.println(entry.getKey() + ":" + entry.getValue());
//        }
     }
}

我们来看一下效果：

========原生Map=======
3:c
2:b
1:a
4:t
========Guava Map=======
3:c
2:b
1:a
5:t
========Guava diff Map=======
3:c
2:b
1:a
========Guava diff Left Map=======
4:t
========Guava diff Right Map=======
5:t
========Guava diff Map=======
b:2
c:3
a:1

好了先写在这，我要去健身房了，回来补上Map的一下排序。。。

好高心昨天在健身房要到了心仪的女生的微信号，好开心好开心，昨天我也是购拼的，昨天为了要微信号在健身房带了4个小时，累死了。

好了今天我们学习以下Map的几种遍历方法：我在今天整理了四种Map的遍历方式，现在原样奉上：

System.out.println("=====第一种Map的Key遍历，遍历Key和Value=====");
//第一种Map的Key遍历，遍历Key和Value
for (String key : map.keySet()) {
    System.out.println("Key : " + key + " and value : " + map.get(key));
} 
//第二种使用entries进行遍历
System.out.println("=====第二种使用entries进行遍历=====");
for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println("Key : " + entry.getKey() + " and value : " + entry.getValue());
} 
//第三种通过Map.entrySet使用iterator遍历key和value
System.out.println("=====第三种通过Map.entrySet使用iterator遍历key和value=====");
Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
while (it.hasNext()){
    Map.Entry<String,String> entry = it.next();
    System.out.println("Key : " + entry.getKey() + " and value : " + entry.getValue());
} 
//第四种获取Map的Key或者Value
System.out.println("=====第四种获取Map的Key=====");
for (String key : guavaMap.keySet()) {
    System.out.println("Key : " + key);
} 
System.out.println("=====第四种获取MapValue=====");
for (String value : guavaMap.values()) {
    System.out.println("value : " + value);
}

看一下结果：

=====第一种Map的Key遍历，遍历Key和Value=====
Key : 3 and value : c
Key : 2 and value : b
Key : 1 and value : a
Key : 4 and value : t
=====第二种使用entries进行遍历=====
Key : 3 and value : c
Key : 2 and value : b
Key : 1 and value : a
Key : 4 and value : t
=====第三种通过Map.entrySet使用iterator遍历key和value=====
Key : 3 and value : c
Key : 2 and value : b
Key : 1 and value : a
Key : 4 and value : t
=====第四种获取Map的Key=====
Key : 3
Key : 2
Key : 1
Key : 5
=====第四种获取MapValue=====
value : c
value : b
value : a
value : t