Write a java program to find average of elements in Hashmap.

Write code to find out the average of all values whose keys are even numbers. Round the average to two decimal places and return as output.

[Hint: If the average is 5.901, the rounded average value is 5.9. The average is 6.333, the rounded average value is 6.33. ]

The return type of the output is a floating-point value which is the average of all values whose key elements are even numbers.

Input and Output Format

• Input consists of the number of elements in the HashMap and the HashMap<int, float>.
• The output is a floating-point value that corresponds to the average.

Refer sample output for formatting specifications

Sample Input 1:

3

1

2.3

2

4.1

6

6.2

Sample Output 1:

5.15

Sample Input 2:

3

9

3.1

4

6.3

1

2.6

Sample Output 2:

6.3

Find the average of elements in Hashmap in Java

Following are the step to find the average of elements:

• Input the size of the HashMap.
• Create an empty HashMap. Add elements to it in key and value pairs.
• Pass the Hashmap to display() method.
• Inside the method, declare and initialize variable sum and count to 0.
• Use the DecimalFormat class to round the decimal place to two digits.
• Now, use the iterator to iterate over the keySet. And check if the key is even. If it is add all keys and at last take the average of them.
• At last, return the average value using the format() method.

import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int s = sc.nextInt();
    HashMap<Integer, Float> hm = new HashMap<Integer, Float>();
    for (int i = 0; i < s; i++) {
      hm.put((sc.nextInt()), sc.nextFloat());
    }
    System.out.println(display(hm));
  }

  public static String display(HashMap<Integer, Float> hm) {
    float sum = 0;
    int count = 0;
    DecimalFormat df = new DecimalFormat("#.00");
    Iterator<Integer> it = hm.keySet().iterator();
    while (it.hasNext()) {
      int y = it.next();
      if (y % 2 == 0) {
        sum = (float) (sum + hm.get(y));
        count++;
      }
    }
    float d = sum / count;
    return df.format(d);
  }
}

Output

How to Sum the Values of a HashMap?

Write code to find out the sum of all values. Round the sum to two decimal places and return as output.

Input and Output Format

• Input consists of the number of elements in the HashMap and the HashMap<int, float>.
• The output is a floating-point value that corresponds to the sum.

Refer sample output for formatting specifications

Sample Input:

3
2
1.2
5
1.2
6
1.2

Sample Output:

3.60

Program to Sum the Values of a HashMap

Following are the step to find out the sum of values in a HashMap:

• Input the size of the HashMap.
• Create an empty HashMap. Add elements to it in key and value pairs.
• Pass the Hashmap to display() method.
• Inside the method, declare and initialize the variable sum to 0.
• Use the DecimalFormat class to round the decimal place to two digits.
• Use for loop, get all the values from the HashMap using values() method, and add it to the sum variable.
• At last, return the sum value using the format() method.

package com.demo3;

import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.Scanner;

public class HashMapProblem {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int s = sc.nextInt();
        HashMap<Integer, Float> hm = new HashMap<Integer, Float>();
        for (int i = 0; i < s; i++) {
            hm.put((sc.nextInt()), sc.nextFloat());
        }
        System.out.println(display(hm));
    }

    public static String display(HashMap<Integer, Float> hm) {
        float sum = 0;
        DecimalFormat df = new DecimalFormat("#.00");
        for(float v: hm.values()){
            sum = sum + v;
        }
        return df.format(sum);
    }
}

Output

Thus, in this way, we learn how to find the average and sum of elements in a HashMap.