您可以使用putAll函数用于Map，如下面的代码所示

HashMap<String, Integer> map1 = new HashMap<String, Integer>();
map1.put("a", 1);
map1.put("b", 2);
map1.put("c", 3);
HashMap<String, Integer> map2 = new HashMap<String, Integer>();
map1.put("aa", 11);
map1.put("bb", 12);
HashMap<String, Integer> map3 = new HashMap<String, Integer>();
map3.putAll(map1);
map3.putAll(map2);
map3.keySet().stream().forEach(System.out::println);
map3.values().stream().forEach(System.out::println);

组合两个可能共享公共键的映射的通用解决方案:

就地:

public static <K, V> void mergeInPlace(Map<K, V> map1, Map<K, V> map2,
        BinaryOperator<V> combiner) {
    map2.forEach((k, v) -> map1.merge(k, v, combiner::apply));
}

返回一个新地图:

public static <K, V> Map<K, V> merge(Map<K, V> map1, Map<K, V> map2,
        BinaryOperator<V> combiner) {
    Map<K, V> map3 = new HashMap<>(map1);
    map2.forEach((k, v) -> map3.merge(k, v, combiner::apply));
    return map3;
}

你可以对其他类型使用Collection.addAll()，例如List, Set等。对于Map，您可以使用putAll。

方法1:将映射放在List中，然后连接

public class Test15 {
public static void main(String[] args) {

    Map<String, List<String>> map1 = new HashMap<>();
    map1.put("London", Arrays.asList("A", "B", "C"));
    map1.put("Wales", Arrays.asList("P1", "P2", "P3"));

    Map<String, List<String>> map2 = new HashMap<>();
    map2.put("Calcutta", Arrays.asList("Protijayi", "Gina", "Gini"));
    map2.put("London", Arrays.asList( "P4", "P5", "P6"));
    map2.put("Wales", Arrays.asList( "P111", "P5555", "P677666"));
    
    System.out.println(map1);System.out.println(map2);
    
    
    
    // put the maps in an ArrayList
    
    List<Map<String, List<String>>> maplist = new ArrayList<Map<String,List<String>>>();
    maplist.add(map1);
    maplist.add(map2);
    /*
<T,K,U> Collector<T,?,Map<K,U>> toMap(

                                  Function<? super T,? extends K> keyMapper,

                                  Function<? super T,? extends U> valueMapper,

                                  BinaryOperator<U> mergeFunction)
    */
    
 Map<String, List<String>> collect = maplist.stream()
    .flatMap(ch -> ch.entrySet().stream())
    .collect(
            Collectors.toMap(
            
            //keyMapper,
            
            Entry::getKey,
            
            //valueMapper
            Entry::getValue,
            
            // mergeFunction
     (list_a,list_b) -> Stream.concat(list_a.stream(), list_b.stream()).collect(Collectors.toList())
            
            ));
    
    
    
    System.out.println("Final Result(Map after join) => " + collect);
    /*
    {Wales=[P1, P2, P3], London=[A, B, C]}
{Calcutta=[Protijayi, Gina, Gini], Wales=[P111, P5555, P677666], London=[P4, P5, P6]}
Final Result(Map after join) => {Calcutta=[Protijayi, Gina, Gini], Wales=[P1, P2, P3, P111, P5555, P677666], London=[A, B, C, P4, P5, P6]}
*/
    
}//main


}

方法二:法线映射合并

public class Test15 {
public static void main(String[] args) {

    Map<String, List<String>> map1 = new HashMap<>();
    map1.put("London", Arrays.asList("A", "B", "C"));
    map1.put("Wales", Arrays.asList("P1", "P2", "P3"));

    Map<String, List<String>> map2 = new HashMap<>();
    map2.put("Calcutta", Arrays.asList("Protijayi", "Gina", "Gini"));
    map2.put("London", Arrays.asList( "P4", "P5", "P6"));
    map2.put("Wales", Arrays.asList( "P111", "P5555", "P677666"));
    
    System.out.println(map1);System.out.println(map2);
    
    
    

    /*
<T,K,U> Collector<T,?,Map<K,U>> toMap(

                                  Function<? super T,? extends K> keyMapper,

                                  Function<? super T,? extends U> valueMapper,

                                  BinaryOperator<U> mergeFunction)
    */
    
    
Map<String, List<String>> collect = Stream.of(map1,map2)
    .flatMap(ch -> ch.entrySet().stream())
    .collect(
            Collectors.toMap(
            
            //keyMapper,
            
            Entry::getKey,
            
            //valueMapper
            Entry::getValue,
            
            // mergeFunction
     (list_a,list_b) -> Stream.concat(list_a.stream(), list_b.stream()).collect(Collectors.toList())
            
            ));
    
    
    
    System.out.println("Final Result(Map after join) => " + collect);
    /*
    {Wales=[P1, P2, P3], London=[A, B, C]}
{Calcutta=[Protijayi, Gina, Gini], Wales=[P111, P5555, P677666], London=[P4, P5, P6]}
Final Result(Map after join) => {Calcutta=[Protijayi, Gina, Gini], Wales=[P1, P2, P3, P111, P5555, P677666], London=[A, B, C, P4, P5, P6]}

*/
    
}//main


}
    

在Python中，HashMap被称为字典，我们可以很容易地合并它们。

x = {'Roopa': 1, 'Tabu': 2}
y = {'Roopi': 3, 'Soudipta': 4}


z = {**x,**y}
print(z)

{'Roopa': 1, 'Tabu': 2, 'Roopi': 3, 'Soudipta': 4}

HashMap有一个putAll方法。

http://download.oracle.com/javase/6/docs/api/java/util/HashMap.html

您可以使用putAll函数用于Map，如下面的代码所示

HashMap<String, Integer> map1 = new HashMap<String, Integer>();
map1.put("a", 1);
map1.put("b", 2);
map1.put("c", 3);
HashMap<String, Integer> map2 = new HashMap<String, Integer>();
map1.put("aa", 11);
map1.put("bb", 12);
HashMap<String, Integer> map3 = new HashMap<String, Integer>();
map3.putAll(map1);
map3.putAll(map2);
map3.keySet().stream().forEach(System.out::println);
map3.values().stream().forEach(System.out::println);