Comparing two hashmaps for equal values and same key sets?

问题

How can I best compare two HashMaps, if I want to find out if none of them contains different keys than the other, and if the values of that keys match each other.

Map<objA, objB> mapA = new HashMap<objA, objB>();
mapA.put("A", "1");
mapA.put("B", "2");

Map<objA, objB> mapB = new HashMap<objA, objB>();
mapB.put("D", "4");
mapB.put("A", "1");

When comparing A with B, it should fail due to different keys B and D.

How could I best compare non-sorted hashmaps?

回答1:

Make an equals check on the keySet() of both HashMaps.

NOTE:

If your Map contains String keys then it is no problem, but if your Map contains objA type keys then you need to make sure that your class objA implements equals().

回答2:

Simply use :

mapA.equals(mapB);

Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings

回答3:

Compare every key in mapB against the counterpart in mapA. Then check if there is any key in mapA not existing in mapB

public boolean mapsAreEqual(Map<String, String> mapA, Map<String, String> mapB) {

    try{
        for (String k : mapB.keySet())
        {
            if (!mapA.get(k).equals(mapB.get(k))) {
                return false;
            }
        } 
        for (String y : mapA.keySet())
        {
            if (!mapB.containsKey(y)) {
                return false;
            }
        } 
    } catch (NullPointerException np) {
        return false;
    }
    return true;
}

回答4:

/* JAVA 8 using streams*/
   public static void main(String args[])
    {
        Map<Integer, Boolean> map = new HashMap<Integer, Boolean>();
        map.put(100, true);
        map.put(1011, false);
        map.put(1022, false);

        Map<Integer, Boolean> map1 = new HashMap<Integer, Boolean>();
        map1.put(100, false);
        map1.put(101, false);
        map1.put(102, false);

        boolean b = map.entrySet().stream().filter(value -> map1.entrySet().stream().anyMatch(value1 -> (value1.getKey() == value.getKey() && value1.getValue() == value.getValue()))).findAny().isPresent();
        System.out.println(b);
    }

回答5:

public boolean compareMap(Map<String, String> map1, Map<String, String> map2) {

    if (map1 == null || map2 == null)
        return false;

    for (String ch1 : map1.keySet()) {
        if (!map1.get(ch1).equalsIgnoreCase(map2.get(ch1)))
            return false;

    }
    for (String ch2 : map2.keySet()) {
        if (!map2.get(ch2).equalsIgnoreCase(map1.get(ch2)))
            return false;

    }

    return true;
}

回答6:

if you have two maps lets say map1 and map2 then using java8 Streams,we can compare maps using code below.But it is recommended to use equals rather then != or ==

boolean b = map1.entrySet().stream().filter(value -> 
            map2.entrySet().stream().anyMatch(value1 -> 
            (value1.getKey().equals(value.getKey()) && 
  value1.getValue().equals(value.getValue())))).findAny().isPresent();   


System.out.println("comparison  "+b);

来源：https://stackoverflow.com/questions/20969211/comparing-two-hashmaps-for-equal-values-and-same-key-sets

标签

java

collections

hashmap

comparison