Find Maximum Element in Each Row of a Matrix in Java

In Java, Array is an object. It is a non-primitive data type which stores values of similar data type. The matrix in java is nothing but a multi-dimensional array which represents multiple rows and columns.

Here we have given a matrix which contains set of elements and as per the problem statement we have to find out the maximum element in each row of that matrix.

Let’s deep dive into this article, to know how it can be done by using Java programming language.

To show you some instances

Instance-1

Given matrix =

21 	22	23
24	25	26
27	28	29

Maximum element in each row: 23, 26 and 29

Instance-2

Given matrix =

121 	222	243	432
124	245	256	657
237	258	229	345
176	453	756	343

Maximum element in each row: 432, 657, 345 and 756

Instance-3

Given matrix =

1 	2	3
4	5	6
7	8	9

Maximum element in each row: 3, 6 and 9

Algorithm

Algorithm-1: (By Using for Loop)

• Step-1 − Use two nested for loops to iterate through the matrix and find the maximum element in each row.

• Step-2 − The outer loop iterates through each row of the matrix, while the inner loop iterates through each element in the row.

• Step-3 − The maximum element in the row is found by using the Math.max method, which returns the larger of two values.

• Step-4 − The result is stored in an array, which is returned at the end.

Algorithm-2: (Using Java Stream)

• Step-1 − Use Java's stream API to find the maximum element in each row.

• Step-2 − The IntStream.range method is used to create a stream of integers from 0 to the number of rows in the matrix.

• Step-3 − The map method is used to apply the function IntStream.of(matrix[i]).max().getAsInt() to each integer in the stream.

• Step-4 − This function returns the maximum element in the row matrix[i] as an integer.

• Step-5 − The result is stored in an array, which is returned at the end.

Syntax

The Matrix.length() method in Java returns the length of the given matrix.

Below refers to the syntax of it −

inputMatrix.lenght

where, ‘inputMatrix’ refers to the given matrix.

IntStream.range() is a method in Java that generates a sequential stream of integers from startInclusive to endExclusive - 1.

IntStream.range(startInclusive, endExclusive)

It can be used to perform operations on a set of integers. For example, in the second code, it is used to loop through the rows and columns of the matrix.

Multiple Approaches

We have provided the solution in different approaches.

• By Using for Loop

• By Using Stream Method

Let’s see the program along with its output one by one.

Approach-1: By Using Nested for Loop

In this approach, matrix elements will be initialized in the program. Then calls a user defined method by passing the matrix as parameter and inside method as per the algorithm using a for loop find maximum element in each row of that matrix.

Example

import java.util.Arrays;
public class Main {
   public static void main(String[] args) {
      int[][] inputMatrix = {{12, 12, 3}, {74, 65, 64}, {57, 28, 49}};
      System.out.println("Max element in each row: ");
      int[] result = maxInEachRow(inputMatrix);
      System.out.println(Arrays.toString(result));
   }
   
   // Method to find the maximum element in each row of the matrix
   public static int[] maxInEachRow(int[][] mat) {
      
      // Array to store the result
      int[] result = new int[mat.length]; 
      
      // Outer loop to iterate through each row of the matrix
      for (int i = 0; i < mat.length; i++) {
         
         // Initialize max to the minimum value of int
         int max = Integer.MIN_VALUE; 
         
         // Inner loop to iterate through each element in the row
         for (int j = 0; j < mat[i].length; j++) {
            
            // Update max with the maximum of the current value and the next element
            max = Math.max(max, mat[i][j]);
         }
         
         // Store the result in the array
         result[i] = max; 
      }
      return result;
   }
}

Output

Max element in each row: 
[12, 74, 57]

Approach-2: By Using Stream Method

In this approach, matrix elements will be initialized in the program. Then calls a user defined method by passing the matrix as parameter and inside method as per the algorithm using stream method find maximum element in each row of that matrix.

Example

import java.util.Arrays;
import java.util.stream.IntStream;
public class Main {
   public static void main(String[] args) {
      int[][] matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
      System.out.println("Max element in each row: ");
      int[] result = maxInEachRow(matrix);
      System.out.println(Arrays.toString(result));
   }
   
   // Method to find the maximum element in each row of the matrix using streams
   public static int[] maxInEachRow(int[][] matrix){
      return IntStream.range(0, matrix.length)
      
      // Get the maximum element in the row
      .map(i -> IntStream.of(matrix[i]).max().getAsInt())
      
      // Convert the stream to an array
      .toArray(); 
   }
}

Output

Max element in each row: 
[3, 6, 9]

In this article, we explored different approaches to find the maximum element in each row of the matrix by using Java programming language.