CODEWITHSUNDEEP
javaalgorithmdata-structureshashmaphashtable
Ram27
Ram27

Reputation: 55

Finding how many number of keys are there in a bucket

When multiple keys have same hash code, then a collision occurs. In that case, key-value entries are stored in linked list format mapping to a bucket. Now I wish to know how many such Map.Entry pair exists for given bucket. Is there any inbuilt java method that would help me to identify?

bucket1 ----> (10, 1) ---> (100, 2) --- Answer is 2 in this case.

bucket2 ----> (2, 1) ---- Answer is 1.

bucket3 ----> (3, 5) ---> (6, 10) ---> (9, 15) ---> (12, 18) ---- Answer in this case 4.

Any help towards this would be great.

Upvotes: 0

Views: 198

Answers (1)

Gregorio Melo
Gregorio Melo

Reputation: 141

Unless you're using a collection as the value for your map, you won't be able to have more than one value for a particular bucket. Check what put() will do in the docs for HashMap

Using a list as value for your map, you can try the following:

import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

public class Playground {

    public static void main(String[] args) {
        Map<Integer, List<Pair>> map = new LinkedHashMap<Integer, List<Pair>>();

        map.put(1, Arrays.asList(new Pair(10, 1) , new Pair(100, 2)));
        map.put(2, Arrays.asList(new Pair(2, 1)));
        map.put(3, Arrays.asList(new Pair(3, 5), new Pair(6, 10), new Pair(9, 15), new Pair(12, 18)));

        for (Map.Entry<Integer, List<Pair>> entry : map.entrySet()) {
            System.out.println(String.format("Bucket %d has %d item(s)", entry.getKey(), entry.getValue().size()));
        }
    }
}

class Pair {
    Integer x;
    Integer y;

    Pair(Integer x, Integer y) {
        this.x = x;
        this.y = y;
    }
}

Your output will be the following:

Bucket 1 has 2 item(s)
Bucket 2 has 1 item(s)
Bucket 3 has 4 item(s)

Hope that helps

Upvotes: 2

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