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Thread: program reads file and prints runs of the same numbers in the form (number of times * number)

  1. #1
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    Default program reads file and prints runs of the same numbers in the form (number of times * number)

    so i need the program to read a file with a list of ints, if there are consecutive equal numbers, such as 10 20 20 20 20 30 30 ... 0, the output should be
    (1 * 10)
    (4 * 20)
    (2 * 30)
    etc, and it will end when a zero is reached

    however im getting an error due to my else if statement and i dont know why?
    can anyone help?

    would an arraylist make i easier?

    import java.util.*;
    import java.io.*;
     
    public class Proj57015 {
     
    public static void main (String [] args) throws FileNotFoundException{
    System.out.println("");
    System.out.println("CMSC 255 - Proj#5 - Jimmy Whitten"); 
     
    String filename = args[0];
    System.out.println("Data File: " + filename);
    System.out.println("");
    Scanner filescan = new Scanner(new File(filename));
     
    int num1 = filescan.nextInt();
    int count = 0;
     
    while (filescan.hasNext()){
    if (num1 == filescan.nextInt())
    count++;
    else if (num1 != filescan.nextInt())
    num1 = filescan.nextInt();
     
    }
    System.out.println("(" + count + "*" + num1 + ")");
     
     
    }
    }

    --- Update ---

    error is:
    exception in thread "main" java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)
    at java.util.Scanner.nextInt(Unknown Source)
    at java.util.Scanner.nextInt(Unknown Source)
    at Proj57015.main(Proj57015.java:27)
    Last edited by jps; November 8th, 2012 at 06:09 AM. Reason: fixed code tag


  2. #2
    Super Moderator curmudgeon's Avatar
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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    When using a Scanner object, there should always be a symmetry if you will between your call to hasNextXXX() and the call to nextXXX(). So if you are call while (myScanner.hasNextFoo()) { inside of that loop there should only be one call to extract information out with the Scanner and it should be trying to extract the same type of information that the hasNext checked, here the fake method myScanner.nextFoo().

    In your code above you check for filescan.hasNext(), which checks the scanner for *any* type token. If you do that, then inside of the loop there needs to be only *one* call to next(). If you want to check for and extract ints, then you should use while (filescan.hasNextInt()), and then call filescan.nextInt() only *once* inside of the block.

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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    ok that makes sense, but then how would i go about assigning the next number of a sequence if i cant call .nextInt again?

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    Super Moderator curmudgeon's Avatar
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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    You store it in a variable that has been declared before the loop.

    Please edit your post and change your [highlight] tags (where'd you get that?) to the proper [code=java] [/code] tags.

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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    sorry, i was wondering why that wasnt working, it said to do that in the "announcements - read if its your first time"

    import java.util.*;
    import java.io.*;
     
    public class Proj57015 {
     
    	public static void main (String [] args) throws FileNotFoundException{
     
    		String filename = args[0];
    		System.out.println("Data File: " + filename);
    		System.out.println("");
    		Scanner filescan = new Scanner(new File(filename));
     
    		int num1 = filescan.nextInt();
    		int count = 0;
     
    		while (filescan.hasNext()){
    			if (num1 == filescan.nextInt())
    				count++;
    			else if (num1 != filescan.nextInt())
    				num1 = filescan.nextInt();
     
    		}
    		System.out.println("(" + count + "*" + num1 + ")");
     
     
    	}
    }

    but if i declared a new int variable outside the loop i couldnt initialize it as anything because id have to use the .nextInt to find when the next run of numbers starts, so wouldnt it just assign the nextInt after my num1 variable?
    Last edited by jslice3; November 8th, 2012 at 02:40 AM.

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    Super Moderator curmudgeon's Avatar
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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    Again, call filescan.nextInt() just *once* inside of the while loop. If this were my code, I'd call the method once and put it into an int variable, and then I could use the int held in the variable as many times as I want.

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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    so something like this?

    import java.util.*;
    import java.io.*;
     
    public class Proj57015 {
     
    	public static void main (String [] args) throws FileNotFoundException{ 
     
    		String filename = args[0];
    		System.out.println("Data File: " + filename);
    		System.out.println("");
    		Scanner filescan = new Scanner(new File(filename));
     
    		int num1 = filescan.nextInt(), num2;
    		int count = 0;
     
    		while (filescan.hasNextInt()){
    			num2 = filescan.nextInt();
    			if (num1 == num2)
    				count++;
    			else 
    				...
     
    		}
    		System.out.println("(" + count + "*" + num1 + ")");
    	}
    }
    Last edited by jslice3; November 8th, 2012 at 02:39 AM.

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    Super Moderator curmudgeon's Avatar
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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    Better for you to test your code yourself. Does the code compile? Does the code work? Does it throw exceptions? Also, please don't double-post your questions as that's not playing fair by the forum rules.

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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    oh yeah I did, and am still working on it, i was just trying to get a visual layout of what you were saying

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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    my input file is ten 20s, five 50s, five 60s, one 20, five 30s, and a 0 in a row
    but my output is
    (1 * 50)
    (1 * 60)
    (1 * 20)
    (1 * 30)
    (0)

    ive read over my code multiple times and still dont know why im getting incorrect results,
    maybe im just missing a simple mistake, but
    any suggestions would be greatly appreciated

    import java.util.*;
    import java.io.*;
     
    public class Proj57015 {
     
    	public static void main (String [] args) throws FileNotFoundException{
     
    		String filename = args[0];
    		System.out.println("Data File: " + filename);
    		System.out.println("");
    		Scanner filescan = new Scanner(new File(filename));
     
    		int num1 = filescan.nextInt(), num2;
    		int count = 1;
     
    		while (filescan.hasNextInt()){
    			num2 = filescan.nextInt();
    			if(num1 == num2)
    				count++;
    			else if(num2 == 0){
    				System.out.println("(0)");
    				System.exit(0);
    			}
    			else if(num1 != num2){
    				count = 1;
    				num1 = num2;
    				System.out.println("(" + count + "*" + num1 + ")");
    			}
    		}
    	}
    }

  11. #11
    Super Moderator jps's Avatar
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    Default Re: program reads file and prints runs of the same numbers in the form (number of times * number)

    It looks like that code will print something almost every time through the loop.
    I would think you need to do all of the counting first so you know what to print, and then print the totals.
    It does not look possible to get an accurate count with the current design. Write down a series of steps to take to solve the problem and then write code to perform the steps.

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