CODEWITHSUNDEEP
javahashmapaverage
Akansha Dahiya
Akansha Dahiya

Reputation: 1

java hashmap values

My hashmap contains a key which is the customers name, and the values are all the ratings for the books rated. I have to calculate the average rating for a given booktitle.

How do I access all of the values (ratings) from the hashmap? Is there a method for doing this?

Here is a piece of my code: 

/** 
 * calculate the average rating by all customers for a named book
 * only count positive or negative ratings, not 0 (unrated)
 * if the booktitle is not found or their are no ratings then
 * return NO_AVERAGE
 * @param booktitle String to be rated
 * @return double the average of all ratings for this book
 */
public double averageRating(String booktitle) 
{ 
    numberOfRatingsPerCustomer/total
}

Upvotes: 0

Views: 1119

Answers (3)

Aamir M Meman
Aamir M Meman

Reputation: 1831

Here you go take these below code it will help you out to find your rating problem I have done to find average of Student marks in a class

import java.util.*;

public class QueQue {

public static float getAverage(HashMap<String, ArrayList<Integer>> hm, String name) {
    ArrayList<Integer> scores;
    scores = hm.get(name);
    if (scores == null) {
        System.out.println("NOT found");
    }

    int sum = 0;
    for (int x : scores) {
        sum += x;
    }
    return (float) sum / scores.size();
}
public static void main(String[] args) {
    HashMap<String, ArrayList<Integer>> hm = new HashMap<>();
    hm.put("Peter", new ArrayList<>());
    hm.get("Peter").add(10);
    hm.get("Peter").add(10);
    hm.get("Peter").add(10);

    hm.put("Nancy", new ArrayList<>());
    hm.get("Nancy").add(7);
    hm.get("Nancy").add(8);
    hm.get("Nancy").add(8);

    hm.put("Lily", new ArrayList<>());
    hm.get("Lily").add(9);
    hm.get("Lily").add(9);
    hm.get("Lily").add(8);

    System.out.println("Find the average of the Peter");
    float num = getAverage(hm, "Peter");

}
  }

Upvotes: 0

dantuch
dantuch

Reputation: 9283

Your question makes no sense.

You can't have a map with customerName to hisRatingOfBook, and search in it for bookTitle. You need to go one of 1 ways:

1) create method public double averageRating() inside Book class, and keep there, as field, rating being map with customerName to hisRatingOfBook

2) Use your method:

public double averageRating(String booktitle) 
{ 
    numberOfRatingsPerCustomer/total
}

but make your map something more complex, that will hold customer, and its rating (being made from book title + rate)

Upvotes: 0

Subir Kumar Sao
Subir Kumar Sao

Reputation: 8401

You need to get the keySet from the HashMap. And then Iterate over the keySet and fetch the values from the HashMap.

Upvotes: 1

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