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Java Collection, HashMap Exercises: Count the number of key-value (size) mappings in a map

Java Collection, HashMap Exercises: Exercise-2 with Solution

Write a Java program to count the number of key-value (size) mappings in a map.

Sample Solution:-

Java Code:

import java.util.*;  
public class Example2 {  
   public static void main(String args[]){  
  HashMap<Integer,String> hash_map= new HashMap<Integer,String>();  
  hash_map.put(1, "Red");
  hash_map.put(2, "Green");
  hash_map.put(3, "Black");
  hash_map.put(4, "White");
  hash_map.put(5, "Blue");
  System.out.println("Size of the hash map: "+hash_map.size());
 }
}

Sample Output:

Size of the hash map: 5 

Java Code Editor:

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Java: Tips of the Day

Choice between Float and Double:

Data type Bytes used Significant figures (decimal)
Float 4 7
Double 8 15

Double is often preferred over float in software where precision is important because of the following reasons:
Most processors take nearly the same amount of processing time to perform operations on Float and Double. Double offers far more precision in the same amount of computation time.

Ref: https://bit.ly/3oj7K2K