Thread: Reading from Text File and Processing Information

Hello I have made a code that can add and subtract two matricies of any size.

The code is:

import java.util.Scanner;
public class MatrixAlgebra
{
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);
 
		//Size of matrix A and B
		int rowsA;
		int colsA;
		int rowsB;
		int colsB;
 
		//decision values
		int operation;
		int dataType;
 
		//matrix A and B
		int[][] aIntMatrix;
		int[][] bIntMatrix;
		int[][] cIntMatrix;
 
		double[][] aDblMatrix;
		double[][] bDblMatrix;
		double[][] cDblMatrix;
 
 
		//get the size of the matrices
		System.out.print("Enter the number of rows and number of columns of matrix A (row column): ");
		rowsA = input.nextInt();
		colsA = input.nextInt();
 
		System.out.print("Enter the number of rows and number of columns of matrix B (row column): ");
		rowsB = input.nextInt();
		colsB = input.nextInt();
 
		//get the datatype of the matrix entries
		System.out.print("To enter integers press 0, for doubles press 1: ");
		dataType = input.nextInt();
 
		//get the operation that will be performed
		System.out.print("To add the matrices enter 0, to subtract the matrices enter 1: ");	
		operation = input.nextInt();
 
			if(dataType == 0)
			{
				aIntMatrix = new int[rowsA][colsA];
				bIntMatrix = new int[rowsB][colsB];
 
				populateMatrix(aIntMatrix, 'A');
				populateMatrix(bIntMatrix, 'B');
 
				switch(operation)
				{
					case 0: 
						cIntMatrix = addMatrix(aIntMatrix, bIntMatrix);
 
						System.out.println("\nA is: ");
						printMatrix(aIntMatrix);
 
						System.out.println("\nB is: ");
						printMatrix(bIntMatrix);
 
						System.out.println("\nC is: ");
						printMatrix(cIntMatrix);
						break;
 
					case 1:
						cIntMatrix = subtractMatrix(aIntMatrix,bIntMatrix);
 
						System.out.println("\nA is: ");
						printMatrix(aIntMatrix);
 
						System.out.println("\nB is: ");
						printMatrix(bIntMatrix);
 
						System.out.println("\nC is: ");
						printMatrix(cIntMatrix);
						break;
				}
 
			}
 
			else if(dataType == 1)
			{
				aDblMatrix = new double[rowsA][colsA];
				bDblMatrix = new double[rowsB][colsB];
 
				populateMatrix(aDblMatrix, 'A');
				populateMatrix(bDblMatrix, 'B');
 
				switch(operation)
				{
					case 0: 
						cDblMatrix = addMatrix(aDblMatrix, bDblMatrix);
 
						System.out.println("\nA is: ");
						printMatrix(aDblMatrix);
 
						System.out.println("\nB is: ");
						printMatrix(bDblMatrix);
 
						System.out.println("\nC is: ");
						printMatrix(cDblMatrix);			
 
						break;
 
					case 1:
						cDblMatrix = subtractMatrix(aDblMatrix,bDblMatrix);
 
						System.out.println("\nA is: ");
						printMatrix(aDblMatrix);
 
						System.out.println("\nB is: ");
						printMatrix(bDblMatrix);
 
						System.out.println("\nC is: ");
						printMatrix(cDblMatrix);
 
						break;
				}
 
			}
	}
 
	// This method is used to populate the two matrices with values (int) entered by the user
	public static void populateMatrix(int[][] a, char matrix)
	{
		Scanner input = new Scanner(System.in);
 
		int row;
		int col;
 
		System.out.println("Enter the rows and columns of matrix " + matrix +": ");
			for(row = 0; row < a.length; row++)
			{
				for(col = 0; col < a[row].length; col++)
				{
					a[row][col] = input.nextInt();
				}
			}
	}
 
 
	// This method is used to populate the two matrices with values (doubles) entered by the user 
	public static void populateMatrix(double[][] a, char matrix)
	{
		Scanner input = new Scanner(System.in);
 
		int row;
		int col;
 
		System.out.println("Enter the rows and columns of matrix " + matrix +": ");
			for(row = 0; row < a.length; row++)
			{
				for(col = 0; col < a[row].length; col++)
				{
					a[row][col] = input.nextDouble();
				}
			}
	}
 
	//This method adds the two matrices (for matrices filled with integers)
	public static int[][]addMatrix(int[][]a, int[][]b)
	{
		int row;
		int col;
		int[][] c = new int[a.length][a[0].length];
 
 
		for(row = 0; row < a.length; row++)	
			for(col = 0; col < a[row].length; col++)
				c[row][col] = a[row][col] + b[row][col];
 
		return c;			
	}
 
	//This method add the two matrices (for matrices filled with doubles)
	public static double[][]addMatrix(double[][]a, double[][]b)
	{
		int row;
		int col;
		double[][] c = new double[a.length][a[0].length];
 
 
		for(row = 0; row < a.length; row++)	
			for(col = 0; col < a[row].length; col++)
				c[row][col] = a[row][col] + b[row][col];
 
		return c;
 
	}
		//This method subtracts the two matrices (for matrices filled with integers)
	public static int[][]subtractMatrix(int[][]a, int[][]b)
	{
		int row;
		int col;
		int[][] c = new int[a.length][a[0].length];
 
 
		for(row = 0; row < a.length; row++)	
			for(col = 0; col < a[row].length; col++)
				c[row][col] = a[row][col] - b[row][col];
 
		return c;			
	}
 
	//This method subtracts the two matrices (for matrices filled with doubles)
	public static double[][]subtractMatrix(double[][]a, double[][]b)
	{
		int row;
		int col;
		double[][] c = new double[a.length][a[0].length];
 
 
		for(row = 0; row < a.length; row++)	
			for(col = 0; col < a[row].length; col++)
				c[row][col] = a[row][col] - b[row][col];
 
		return c;
	}
 
	//This method prints the two matrices input by the user and the calculated matrix C
	public static void printMatrix(int[][] matrix)
	{
		int row;
		int col;
 
		for(row = 0; row < matrix.length; row++)
			{
				for(col = 0; col < matrix[row].length; col++)									
					System.out.printf("%5d", matrix[row][col]);
 
				System.out.println();
			}
	}
 
	public static void printMatrix(double[][] matrix)
	{
		int row;
		int col;
 
		for(row = 0; row < matrix.length; row++)
			{
				for(col = 0; col < matrix[row].length; col++)									
					System.out.printf("%5.2f", matrix[row][col]);
 
				System.out.println();
			}
	}
}

Now instead of asking for user input, the input needs to come from a txt file and an output file needs to be written. How would I approach editing the code to extract the information?

The input.txt will look like

int (<< data type)
4 6 (<< row by column)
(random numbers go here)