Subtraction of Two Matrix in Java

Subtraction of Two Matrix in Java | Program description:- Write a Java program to find the subtraction of two matrix. Take two matrices, declare the third matrix to store the result value.

Let A =[a_ij] and B =[b_ij] be m × n matrices. The subtract of A and B, denoted by A – B, is the m × n matrix that has a_ij – b_ij as its (i, j)th element. In other words, A – B =[a_ij – b_ij].

The subtraction of two matrices of the same size is obtained by subtracting elements in the corresponding positions. 

Condition for finding subtraction of two matrix in Java :- Both matrices should have same size.

Matrices of different sizes cannot be subtracted, because the subtraction of two matrices is defined only when both matrices have the same number of rows and the same number of columns.

    a11 a12
A =
    a21 a22

    b11 b12
B =
    b21 b22

The subtraction of A and B can be calculated as,

        a11-b11 a12-b12
A - B =
        a21-b21 a22-b22

Before solving this problem, you should have knowledge of how to declare and initialize a matrix in Java, how to take input for a matrix from the end-user, and what are the different ways to display it. How to find the length or size of a matrix in Java? How to pass and return a matrix in Java. See:- Matrix in Java

Java Program to Find the Subtraction of Two Matrix

import java.util.Scanner;

public class Matrix {
  
  // create Scanner class object to read input
  private static Scanner scan = new Scanner(System.in);

  // main method
  public static void main(String[] args) {
    
    // declare variables
    int row = 0;
    int column = 0;
    int a[][] = null; // first matrix
    int b[][] = null; // second matrix
    int c[][] = null; // resultant matrix
    
    // ask row and column size
    System.out.println("Enter row and column size: ");
    row = scan.nextInt();
    column = scan.nextInt();

    // initialize matrices
    a = new int[row][column];
    b = new int[row][column];
    c = new int[row][column];
    
    // read matrix A and B
    System.out.println("Enter Matrix A: ");
    a = readMatrix(a);
    System.out.println("Enter Matrix B: ");
    b = readMatrix(b);

    // Subtraction of matrix
    c = subMatrix(a, b);

    // display resultant matrix
    System.out.println("Subtraction (C): ");
    for(int i=0; i<c.length; i++) {
      for(int j=0; j<c[0].length; j++) {
        System.out.print(c[i][j]+" ");
      }
      System.out.println(); // new line
    }
  }
  
  // method to read matrix elements as input
  public static int[][] readMatrix(int[][] temp) {
    for(int i=0; i<temp.length; i++) {
      for(int j=0; j<temp[0].length; j++) {
        // read matrix elements
        temp[i][j] = scan.nextInt();
      }
    }
    return temp;
  }

  // method to calculate the subtraction of two matrix
  public static int[][] subMatrix(int[][] a, int[][] b) {
    // calculate row and column size
    int row = a.length;
    int column = a[0].length;
    
    // declare a matrix to store resultant
    int sub[][] = new int[row][column];
    
    // calculate subtraction of two matrices
    // outer loop for row
    for(int i=0; i<row; i++) {
      // inner loop for column
      for(int j=0; j<column; j++) {
        // formula
      sub[i][j] = a[i][j] - b[i][j];
      }
    }
    
    // return resultant matrix
    return sub;
  }

}

Output:-

Enter row and column size:
3 3
Enter Matrix A:
20 19 18
17 16 15
14 13 12
Enter Matrix B:
10 11 12
13 15 15
10 11 10
Subtraction (C):
10 8 6
4 1 0
4 2 2

In this program, we had created the Scanner class object as a private static variable which is outside of the main method because we need to read input values in two methods, in the main method to read row and column values and in readMatrix() method to read matrix elements. Therefore instead of creating Scanner class objects in both classes separately, it is better to create them as a static variable only once and use it multiple times anywhere in the program.

See more matrix programs in Java:- 

1. Program to Print 3×3 Matrix 
2. Sum of matrix elements in Java
3. Sum of Diagonal Elements of Matrix in Java 
4. Matrix Addition in Java
5. Subtraction of two matrices in Java 
6. Transpose of a Matrix in Java 
7. Matrix Multiplication in Java
8. Menu-driven program for Matrix operations to perform matrix addition subtraction multiplication and transpose.

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