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Java Matrix Transpose Program (3 Ways to Transpose Matrix)

Matrices are fundamental mathematical structures used in various fields, including computer science and engineering. The transpose of a matrix is a simple but important operation that involves flipping a matrix over its diagonal, resulting in a new matrix where rows become columns and columns become rows. 

Transposition is a valuable tool in matrix algebra, as it has applications in tasks such as solving systems of linear equations, calculating determinants, and performing various transformations in computer graphics and data analysis.

In this tutorial, we will learn how to find the transpose of a matrix in Java. We will start with the basics, explaining the concept of matrix transposition and its significance. Then, step by step, we will dive into the implementation of a Java program to perform this operation.

Concepts of Java Used:

Transpose of a Matrix in Java Using Scanner

Here's a Java program to find the transpose of a matrix with user input, using scanner and nested loops:

Code

import java.util.Scanner;

public class MatrixTranspose {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        
        // Input matrix dimensions
        System.out.print("Enter the number of rows: ");
        int rows = input.nextInt();
        System.out.print("Enter the number of columns: ");
        int cols = input.nextInt();
        
        int[][] matrix = new int[rows][cols];
        
        // Input matrix elements
        System.out.println("Enter the matrix elements:");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                matrix[i][j] = input.nextInt();
            }
        }
        
        // Transpose the matrix
        int[][] transpose = new int[cols][rows];
        for (int i = 0; i < cols; i++) {
            for (int j = 0; j < rows; j++) {
                transpose[i][j] = matrix[j][i];
            }
        }
        
        // Display the original matrix
        System.out.println("Original Matrix:");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }
        
        // Display the transposed matrix
        System.out.println("Transpose Matrix:");
        for (int i = 0; i < cols; i++) {
            for (int j = 0; j < rows; j++) {
                System.out.print(transpose[i][j] + " ");
            }
            System.out.println();
        }
        
        input.close();
    }
}

Output

Enter the number of rows: 3
Enter the number of columns: 4
Enter the matrix elements:
1 2 3 4
5 6 7 8
9 10 11 12

Original Matrix:
1 2 3 4 
5 6 7 8 
9 10 11 12 

Transpose Matrix:
1 5 9 
2 6 10 
3 7 11 
4 8 12

Explanation

  • We start by taking user input for the number of rows and columns in the matrix.

  • Then, we create a 2D array to store the matrix elements and populate it with user input.

  • Next, we create another 2D array for the transpose of the matrix and use nested loops to calculate the transpose by swapping rows and columns.

  • Finally, we display both the original and transposed matrices to the user.

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Matrix Transpose in Java Using Arrays.copyOf()

Here's a program to find the transpose of a matrix in Java with user input, using the Arrays.copyOf() method:

Code

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

public class MatrixTransposeCopyOf {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        
        // Input matrix dimensions
        System.out.print("Enter the number of rows: ");
        int rows = input.nextInt();
        System.out.print("Enter the number of columns: ");
        int cols = input.nextInt();
        
        int[][] matrix = new int[rows][cols];
        
        // Input matrix elements
        System.out.println("Enter the matrix elements:");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                matrix[i][j] = input.nextInt();
            }
        }
        
        // Transpose the matrix using Arrays.copyOf()
        int[][] transpose = new int[cols][rows];
        for (int i = 0; i < cols; i++) {
            transpose[i] = Arrays.copyOf(matrix[i], rows);
        }
        
        // Display the original matrix
        System.out.println("Original Matrix:");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }
        
        // Display the transposed matrix
        System.out.println("Transpose Matrix:");
        for (int i = 0; i < cols; i++) {
            for (int j = 0; j < rows; j++) {
                System.out.print(transpose[i][j] + " ");
            }
            System.out.println();
        }
        
        input.close();
    }
}

Output

Enter the number of rows: 3
Enter the number of columns: 4

Enter the matrix elements:
1 2 3 4
5 6 7 8
9 10 11 12

Original Matrix:
1 2 3 4 
5 6 7 8 
9 10 11 12 

Transpose Matrix:
1 5 9 
2 6 10 
3 7 11 
4 8 12

Explanation

  • We start by taking user input for the number of rows and columns in the matrix, similar to the previous method.

  • We create a 2D array to store the matrix elements and populate it with user input.

  • Next, we create another 2D array for the transpose of the matrix. Instead of using nested loops to calculate the transpose, we use the Arrays.copyOf() method to copy rows from the original matrix to the transposed matrix, effectively swapping rows and columns.

  • Finally, we display both the original and transposed matrices to the user, producing the desired output.

Transpose of a Matrix in Java Using Library

To find the transpose of a matrix using the Apache Commons Math library, you'll need to add the library as a dependency. Here's a Java program to find the transpose of a matrix using Apache Commons Math:

Code

import org.apache.commons.math3.linear.MatrixUtils;
import org.apache.commons.math3.linear.RealMatrix;
import org.apache.commons.math3.exception.MathIllegalArgumentException;

public class MatrixTransposeCommonsMath {
    public static void main(String[] args) {
        int[][] matrixData = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};

        // Create a RealMatrix from the matrix data
        RealMatrix matrix = MatrixUtils.createRealMatrix(matrixData);

        // Transpose the matrix
        RealMatrix transpose = matrix.transpose();

        // Display the original matrix
        System.out.println("Original Matrix:");
        printMatrix(matrix);

        // Display the transposed matrix
        System.out.println("Transpose Matrix:");
        printMatrix(transpose);
    }

    // Utility method to print a RealMatrix
    private static void printMatrix(RealMatrix matrix) {
        int rows = matrix.getRowDimension();
        int cols = matrix.getColumnDimension();

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                System.out.print(matrix.getEntry(i, j) + " ");
            }
            System.out.println();
        }
    }
}

Output

Original Matrix:
1.0 2.0 3.0 
4.0 5.0 6.0 
7.0 8.0 9.0 

Transpose Matrix:
1.0 4.0 7.0 
2.0 5.0 8.0 
3.0 6.0 9.0

Explanation

  • In this program, we define the matrix data as a 2D array called matrixData.

  • We create a RealMatrix object using the MatrixUtils.createRealMatrix(matrixData) method from the Apache Commons Math library. This creates a matrix from the given data.

  • To find the transpose, we simply call the transpose() method on the RealMatrix object, which returns a new RealMatrix representing the transpose of the original matrix.

  • We use a utility method called printMatrix to print both the original and transposed matrices.

  • The output demonstrates the original and transposed matrices.

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