Skip to main content

How to Calculate median in Java? | With Array and List | Programming Blog

Find median of Java Array and List values using 2 ways

Find median of Java Array and List values using 2 ways

What is Median?

Median is mid value of particular data set. This data set must be sorted. 

In simple word, Median is mid value of sorted data.

Median will be middle, if total number of elements is odd or average of middle elements when total number of elements is even.

Example :

When total number of elements are odd

1, 2, 3, 4, 5, 6, 7
Median will be : 4

2, 3, 5, 7, 8
Median will be : 5

When total number of elements are even

1, 2, 3, 4
Median will be : (2+3) / 2 : 2.5

2, 4, 6, 8, 10, 20, 25, 30
Median will be : (8+10) / 2 : 9

So the formula become for our code :

For odd elements :

Median = (Total length / 2)

For even elements :

Median = (Total length / 2) + (Total length / 2 - 1) / 2

So lets jump on code. We will take elements form user.

Method 1 : Using code logic

In this approach, we does not use any library function for find median.

Example 1 : Find median from Java array

import java.util.Arrays;
import java.util.Scanner;

public class FindTheMedian {

    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter total elements length");
        int length = sc.nextInt();
        int[] array = new int[length];
        System.out.println("Enter elements");
        for (int i = 0; i < length; i++) {
            array[i] = sc.nextInt();
        }
        
        // Sort the Array
        Arrays.sort(array);
        double median = 0;
        
        // When total length is Even
        if (length % 2 == 0) {
            median = ((double) array[length/2] + (double) array[(length/2) - 1]) / 2;
        
        // When total length is Odd
        } else {
            median = (double) array[length/2];
        }
        
        System.out.println("Median is : "+median);
    }
}

Output :

Enter total elements length
6
Enter elements
2 4 6 8 10 15
Median is : 7.0

Enter total elements length
5
Enter elements
1 2 3 4 5
Median is : 3.0

Example 2 : Find median from Java List

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

public class FindTheMedian {

    public static void main(String[] args) {
       
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter total elements length");
        int length = sc.nextInt();
       
        System.out.println("Enter elements");
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < length; i++) {
            list.add(sc.nextInt());
        }
       
        // Sort the List
        Collections.sort(list);
        double median = 0;
       
        // When total length is Even
        if (length % 2 == 0) {
            median = ((double)list.get(length/2) + (double)list.get((length/2)-1)) / 2;
        }
       
        // When total length is Odd
        else {
            median = (double)list.get(length/2);
        }

        System.out.println("Median is : "+median);
    }
}

Output :

Enter total elements length
8
Enter elements
5 1 6 8 10 0 2 7
Median is : 5.5

Enter total elements length
5
Enter elements
90 10 8 50 15
Median is : 15.0

Method 2 : Using Apache commons library

This problem can also solve by Apache commons Math library. 

org.apache.commons.math3.stat.descriptive.rank.Median package provides solution for evaluate median of array.

We must have to use double array for use this library. lets see how ii works.

import java.util.Scanner;

import org.apache.commons.math3.stat.descriptive.rank.Median;

public class FindTheMedian {

    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter total elements length");
        int length = sc.nextInt();
        double[] array = new double[length];
        
        System.out.println("Enter elements");
        for (int i = 0; i < length; i++) {
            array[i] = sc.nextDouble();
        }
        
        Median median = new Median();
        double answer = median.evaluate(array);
        System.out.println(answer);
    }
}

Output :

Enter total elements length
6
Enter elements
10 15 8 4 9 7
8.5

Enter total elements length
5
Enter elements
9 7 2 5 1
5.0

 

Other articles :

 

Comments

Post a Comment

Popular posts from this blog

Flipping the Matrix HackerRank Solution in Java with Explanation

Java Solution for Flipping the Matrix | Find Highest Sum of Upper-Left Quadrant of Matrix Problem Description : Sean invented a game involving a 2n * 2n matrix where each cell of the matrix contains an integer. He can reverse any of its rows or columns any number of times. The goal of the game is to maximize the sum of the elements in the n *n submatrix located in the upper-left quadrant of the matrix. Given the initial configurations for q matrices, help Sean reverse the rows and columns of each matrix in the best possible way so that the sum of the elements in the matrix's upper-left quadrant is maximal.  Input : matrix = [[1, 2], [3, 4]] Output : 4 Input : matrix = [[112, 42, 83, 119], [56, 125, 56, 49], [15, 78, 101, 43], [62, 98, 114, 108]] Output : 119 + 114 + 56 + 125 = 414 Full Problem Description : Flipping the Matrix Problem Description   Here we can find solution using following pattern, So simply we have to find Max of same number of box like (1,1,1,1). And ...
Post a Comment
Read more

How to Implement One to Many and Many to One Mapping in Spring Boot using JPA

Spring Boot CRUD example using One-to-Many and Many to One mapping | With Thymeleaf User Interface In this tutorial, we will learn how to use @OneToMany and @ManyToOne annotation using JPA (Java Persistent API) in Spring Boot. We also attach Thymeleaf for User Interface. In past tutorial, we already created Spring Boot CRUD with Rest API, JPA and MySql. Please refer that one first, we will continue from there. Spring Boot application with Thymeleaf, Rest API, JPA and MySql Database    For applying One to Many relationship, we need another POJO class. In past we already created Book class, now we will create new class Author . As we know Author have multiple Books, so we can easily apply One to Many operation. Lets create POJO class for Author and apply @OneToMany on Book .  Define List of Book and apply @OneToMany annotation on field. We are using mappedBy property, so Author table does not create new column.  We already learn about mappedBy property in One-to-One a...
Post a Comment
Read more