CODEWITHSUNDEEP
javahashmapbag
emmynaki
emmynaki

Reputation: 157

calculating frequency of an element in hashmap

I'm implementing a bag using a hashmap and I'm trying to calculate the frequency of an element in my hashmap and I keep getting one less than what it should be.

this is my map 

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

this is my add method 

 public void add(int element) {
 //containsKey 
 //checks if the element is already there 
 if (map.containsKey(element)){ 
    Integer numElt = map.get(element);
    map.put(element, (numElt+1)); //line where it should increment number of keys if the element is already there 
    count++; 
 }

 else { 
    map.put(element, 1); 
    count++; 
 }
}

and my frequency 

public int freq(int element) {
 Integer numE = map.get(element); 
 int k = Collections.frequency(map.values(), numE); 
 return k;

}

if I write my test like so 

Bag b = new Bag(): 
b.add(4)
b.add(5)
b.add(5)

assertTrue(2, b.freq(5))

should return 2 but it's returning 1. Not sure why that is and I'm sorry if it seems like an obvious error I'm new to bag implementation

Upvotes: 1

Views: 5193

Answers (1)

leonz
leonz

Reputation: 1127

Ok, if I understood your question you want the value of an element in the map. So if you have a map that is {4 : 1, 5 : 2}, freq(5) should be 2 and freq(4) should be 1. I'm not sure why are you using Collections.frequency, check the documentation, that method returns number of values in a collection. So for any key in a map it will return 1, as map cannot contain duplicate keys. What you need is this:

public int freq(int element) {
    return map.get(element);
}

Upvotes: 3

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