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Thread: Reading from Text File and Processing Information

  1. #1
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    Default 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)
    Last edited by royalslim; December 13th, 2010 at 02:09 PM.


  2. #2
    Super Moderator copeg's Avatar
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    Default Re: Reading from Text File and Processing Information

    See Java IO Turorial for how to work with files.

  3. #3
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    Default Re: Reading from Text File and Processing Information

    Quote Originally Posted by copeg View Post
    See Java IO Turorial for how to work with files.
    Theres going to be an InputA.txt (First Matrix) and InputB.txt (Second Matrix). The user will need to specify the name of these two files. So how would you recommend I use Scanner to replace where I got input the first way?

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