CODEWITHSUNDEEP
javahashmap
absoluz7
absoluz7

Reputation: 30

HashMap Duplicate Values - find number of duplicates

I have a HashMap variable called map were the key is an Integer and the value is a String.

Say for example that there are 100 values in map. I want to search the 100 values for "Donkey" and then I want to return an Integer with the number of "Donkey" in map if there are none then return Integer 0. I tried to use a for loop with map.values() but no luck.

Can someone give me a hint please?

Upvotes: 0

Views: 4870

Answers (2)

KevinO
KevinO

Reputation: 4403

The Collections.frequency approach is a nice one. However, the assertion that the map.values() didn't work is a bit strange, as it should work. I would add it is especially strange since the Collection passed to the Collections.frequency is the map.values().

// method to do the counting of a particular animal in a map
static Integer countAnimal(String animal, Map<Integer, String> map)
{
    int cnt = 0;
    for (String val : map.values()) {
        if (val.equals(animal)) {
            ++cnt;
        }
    }

    return new Integer(cnt);
}

public static void main(String[] args)
{
    String[] animals = new String[] { "cat", "dog", "pig", "goat", "donkey", "horse", "cow" };

    Map<Integer, String> map = new HashMap<>();

    // load map for test
    Random rnd = new Random();
    for (int i = 0; i < 100; ++i) {
        String animal = animals[rnd.nextInt(animals.length)];
        map.put(new Integer(i), animal);
    }

    // count how many there are
    Map<String, Integer> numAnimals = new HashMap<>();

    for (String animal : animals) {
        numAnimals.put(animal, countAnimal(animal, map));
    }

    System.out.println(numAnimals);

    // show the cool Collections.frequency approach
    Integer count = Collections.frequency(map.values(), "dog");
    System.out.println("dog: " + count);
}

Example output:

{horse=18, cat=13, donkey=23, cow=15, goat=17, dog=3, pig=11}
dog: 3

EDIT: an update that allows splitting a string to find the count. Basically countAnimal will split the String retrieved from the map, and then check each token to see if it is an animal. Changed the test case slightly as well. It works based upon the updated comment. It does not consider, however, plurals. The trivial case of "cat" and "cats" is easily handled, but "mouse" and "mice" would be more difficult, and require additional work.

public static void main(String[] args)
{
    String[] animals = new String[] { "cat", "dog", "pig", "goat",
            "donkey", "horse", "cow" };

    Map<Integer, String> map = new HashMap<>();

    // load map for test
    map.put(1, "My friend has a horse");
    map.put(2, "A bear can be big"); // will not be found
    map.put(3, "A cat is a loner");
    map.put(4, "A dog is man's best friend");
    map.put(5, "The cat and the dog are peacefully sleeping");

    // count how many there are
    Map<String, Integer> numAnimals = new HashMap<>();

    for (String animal : animals) {
        numAnimals.put(animal, countAnimal(animal, map));
    }

    System.out.println(numAnimals);
}



static Integer countAnimal(String animal, Map<Integer, String> map)
{
    int cnt = 0;
    for (String val : map.values()) {
        // split the val by space
        String[] tokens = val.split("[\\s]+");
        for (String token : tokens) {
            if (token.equalsIgnoreCase(animal)) {
                ++cnt;
            }
        }
    }

    return new Integer(cnt);
}

Example output:

{horse=1, cat=2, donkey=0, cow=0, goat=0, dog=2, pig=0}

Upvotes: 0

Vijay Mohan
Vijay Mohan

Reputation: 1066

Try this:

int count = Collections.frequency(mapVar.values(), "Donkey");
System.out.println(count);

Let me know whether its worked :)

Upvotes: 4

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