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Thread: Simple I/O Java Error

  1. #1
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    Default Simple I/O Java Error

    Im supposed to write this java program, and im having a problem, and I cannot figure out why I am getting an Unhandled Exception error.

    I put a comment at the error line.

    PrintWriter writer = new PrintWriter (writingfile); (Line where I am getting uNhandled exception error.)



    Write a program that reads numeric operations from a
    file and writes their result into another file.

    Numbers & results are integer.
    • Operators (+ - * / ) have equal precedence.
    • Input file
    • Name: “input.txt”
    • There can be many operations, each on its own line, e.g.,
    2 + 3 * 10 / 2
    10 / 3 * 2
    • Output file
    • Name: “output.txt”
    • The result of each operation is written in one line, e.g.,
    25

    Code ~

    import java.io.File;
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.ArrayList;
    import java.util.Scanner;
     
    //There is NO PRECEDENCE in the math from the file
    public class Operations {
    public static void main (String [] args) {
     
    	ArrayList<String> inputs = new ArrayList<String>();	
    int [] array = new int[10]; //change this once the add to method works.
    String k = "";
     
    	try {	
     
    		File inputfile = new File("math.txt");
    		Scanner in = new Scanner (inputfile);
    	while (in.hasNextLine()) {
    		inputs.add (in.nextLine() );
    	}
    	in.close(); //all objects are inside of the ArrayList String type
     
    	for (int i = 0; i < inputs.size(); i++) { //attempting to change from String to int
    		k = inputs.get(i);
    		array[i] = Integer.parseInt(k);
     
    	}
    		}
     
    			catch (IOException e) {
    			System.out.println("You done fucked up real good.");
    	}
     
    	File writingfile = new File ("output.txt");  //Writing to the file
    	PrintWriter writer = new PrintWriter (writingfile);
     
    	for (int i =0; i < array.length; i++ ) {
     
     
     
    		writer.println(array[i]);
    	}
    	writer.close();
    	}
     
     
    	}


    The file I ma reading the ints from looks like this. (named math.txt)

    1+2*3/3
    1+2+3+4*3/3
    1+2+4

    Help would be awesome. Thanks.
    Last edited by Prox; October 25th, 2011 at 11:02 AM.


  2. #2
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    Default Re: Simple I/O Java Error

    I think you are wrong in this line:
    array[i] = Integer.parseInt(k);

    "*,/,+,-" may could not be parsered into an int.

  3. #3
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    Default Re: Simple I/O Java Error

    So then how would go about parsing the operators when you are reading the files from an input file?

  4. #4
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    Default Re: Simple I/O Java Error

    You do not need to parse the operators. You can leave them as a String or use charAt to get then as a char.
    Improving the world one idiot at a time!

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