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Thread: Read txt file into array and create new output.

  1. #1
    Junior Member
    Join Date
    Nov 2011
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    Exclamation Read txt file into array and create new output.

    What I need to do is create a class that creates a text file of an array. (Which I have posted Below)

    What I need help with

    Once that file is created I need to create a class that reads the numbers that were created and then multiplies all the numbers by the number at position [0][0]. Then creates a new .txt file and puts them in there.

    Original numbers
    5 6 3 4

    Output needs to be
    25 30 15 20

    I have a class that reads the numbers and just prints them out. I cant figure out how to read the numbers and do anything with them.

    Code that creates file with array of numbers.....
    import java.io.*;
    import java.util.Random;
    public class Output
     public static void main(String args[])
    	 final int rowW = 2;
    	 final int colH = 4;
    	 Random rand = new Random();
    	 int [][] array1 = new int [rowW][colH];
    	 for (int row = 0; row < array1.length; row++) {
    	     for (int col = 0; col < array1[row].length; col++) {
    	             array1[row][col] = rand.nextInt(10);
    	  FileWriter  fStream;
    	   PrintWriter  myStream;
    	   fStream = new FileWriter( "randomarray.txt");
    	   myStream = new PrintWriter( fStream );
    	   int l= array1.length;
    	   for(int i = 0; i < l; i++) {
    	   for(int j = 0; j <= l; j++) {
    	   myStream.print( " "+ array1[i][j] );
    	catch (IOException e)  {
    	   System.out.println("I/O exception" );

    Just reads the array and prints it out. I need it to read the numbers and then be able to multiply them and create a new file with multiplied numbers. (I could just add them to the bottom of the original file if that is possible)
    import java.io.*;
    class input {
        public static void main(String[] args) {
        	try {
        		   FileReader  fReader;
        		   BufferedReader  reader;
        		   int  charAsInt;
        		   fReader = new FileReader("randomarray.txt");
        		   reader = new BufferedReader( fReader );
        		   charAsInt = reader.read();
        		   while ( charAsInt != -1 )   {
        		      System.out.print( (char)charAsInt); 
        		      charAsInt = reader.read();
        		catch (IOException e)  {
        		   System.out.println( "I/O exception" );

    Thanks in advance for any help

  2. #2
    Super Moderator Norm's Avatar
    Join Date
    May 2010
    Eastern Florida
    Thanked 2,710 Times in 2,660 Posts

    Default Re: Read txt file into array and create new output.

    how to read the numbers and do anything with them.
    The Scanner class has methods that will read from a text file and convert the String that was read to an int or double value.
    The read() method reads bytes from the file and will require you to do some work to convert those bytes back to the number. The Scanner class methods will be much easier to use.
    If you don't understand my answer, don't ignore it, ask a question.

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