Manipulating Vectors (code not working)

[John Lockheart]

I'm trying to read data from a text file and manipulate a vector accordingly. The first two digits correspond to row and column of the vector to be created. Each number afterwards is supposed to be stored, each string skipped (producing an error message), and in the case of 6*-7 (stores -7, 6 times). The only thing i'm getting out of my code is a vector containing all zeroes. None of the integers are being stored, nor is it handling the special case, or producing an error message when it encounters a string. You can compile the following code in an editor, it's a working example (well not technically a "working" example). This is the first time i've worked with Tokenizer, and thats the part which i think is screwing things up.

File.txt
--------
5 3
1 2 -3
4 five 6*-7 8
 
9 ten !*! 11

import java.util.*;
import java.util.StringTokenizer;
import javax.swing.JOptionPane;
import java.io.*;
 
public class MatrixManipulation {
    public static void main(String[] args) {
 
    MatrixFill("a4q1.txt");
 
    }
 

public static void MatrixFill(String filename){
 
int rows = 0,
columns = 0,
x = 0,
y = 0,
int1,
int2;
 
int[][] matrix = null;
 
String line,
   token,
   token2;
 
boolean specialCase = false;
 
StringTokenizer tokenizer,
tokenizer2;
 
    BufferedReader input = null;
 
        try {
 
            input = new BufferedReader(new FileReader(filename));
line = input.readLine();
 
tokenizer = new StringTokenizer(line);
 
rows = Integer.parseInt(tokenizer.nextToken());
columns = Integer.parseInt(tokenizer.nextToken());
 
matrix = new int[rows][columns];
 
while (line != null) {//process none blank lines
 
    //code doesn't seem to get past here
    while(tokenizer.hasMoreTokens() == true) {//process tokens
 
    token = tokenizer.nextToken();
 
    while(x<=matrix.length){//x can equal rows, but not be greater than
 
    try{
 
    if(y == columns){//y has reached last column, increase rows and restart from column 0
y = 0;
x++;
}
 
    matrix[x][y] = Integer.parseInt(token); //assign tokens to vector
y++;
 

}catch (NumberFormatException e){
 
 for(int i=0; i<token.length(); i++){
 
if(token.charAt(i) == '*'){//search for special case "*"
specialCase = true;
}
 
specialCase = false;
 }
 
 if(specialCase == true){
 tokenizer2 = new StringTokenizer(token, "*");
 
 try{
 
 int1 = Integer.parseInt(tokenizer2.nextToken()); //# of repetitions
 int2 = Integer.parseInt(tokenizer2.nextToken()); //Integer to be stored
 
 for(int i=0; i<int1; i++){
 
if(y == columns){
y = 0;
x++;
}
 
matrix[x][y] = int2; //assign integer to token (x many times)
y++;
 

}
 
 }catch (NumberFormatException nfe){
 
JOptionPane.showMessageDialog(null, "Invalid Entry");
 }
 
 }
 
JOptionPane.showMessageDialog(null, "Invalid Entry");
 
}
 
}
 
}
 
 line = input.readLine();
            }
 
        } catch (FileNotFoundException e) {
            System.out.println("Unable to open file " + filename);
        } catch (IOException e) {
            System.out.println("Unable to read from file " + filename);
        }finally {
 
        // Close the file
        try {
           if (input != null)
           input.close();
        } catch (IOException e) {
           System.out.println("Unable to close file " + filename);
        }
 
     }
 
//print vector
for(int row=0; row<matrix.length; row++){
 
for(int col=0; col<matrix[0].length; col++){
 
System.out.print(matrix[row][col]);
 
}
}
 
    }
}
 

[Christophe Verré]

Here are a few tips to begin with

1. You're not reading the line at the right place. I think you should read the line like:
while ((line = input.readLine()) != null)
2. You have to rebuild a new tokenizer each time
tokenizer = new StringTokenizer(line);

I didn't look at the logic where you put values in the array
(we usually don't call [][] vectors, but two-dimension arrays)

[John Lockheart]

#1. ((line = input.readLine()) != null) is exactly what i have (written in a diffrent fashion). I have line = input.readLine(); and then underneath it I have the while loop using line as a condition.

#2.tokenizer = new StringTokenizer(line); I have that line of code directly underneath my while loop, so that's exactly what happens every time.

I appologise for the confusion, i meant two-dimensional arrays.

The biggest problem i have is creating the two dimensional array based on the first two tokens from the file (5 and 3), then reading the rest of the tokens and storing them.

[Christophe Verré]

Ok, forget about #1, as I got a bit confused

About #2, you still need to rebuild a StringTokenizer after reading a line.
If I were you, I'd the other way around :

while ((line = input.readLine()) != null) {//process none blank lines
  tokenizer = new StringTokenizer(line);
  ...
}

Tips: if you can't use a debugger, add a few println here and there to see what your program is doing.

[John Lockheart]

ya i noticed that, i strung together the program and compiled it, made a few modifications after I noticed how I wrote it. That was one of the modifications. After using the print statements, all of my tokens come out fine. Now i'm confronted with, using the first two ints as parameters for my two dimensional array. and then storing the rest of them (dealing with strings and the case i mentioned). I'm not sure whats wrong with the code after the while(x<matrix.length-1).

[Christophe Verré]

Here is a sample to put the numbers into the array.
As this sounds like an assignment, I'll leave you deal with the special tokens. If you use a few println, you should be able to figure it out

while ((line = input.readLine()) != null) {

line = line.trim();
if ( line.length() == 0 ) {
// skip blank line
continue;
}
 
tokenizer = new StringTokenizer(line);
 
x  = 0;
    while(tokenizer.hasMoreTokens() == true) {
 
    token = tokenizer.nextToken();
    System.out.println("Token: " + token );     

try { 
int value = Integer.parseInt(token);
matrix[y][x++] = value;
} catch (NumberFormatException e) {
if ( token.indexOf("*") != -1 ) {
System.out.println("Special token");
}
}
 
}
y++;
}
 
for(int row=0; row<matrix.length; row++){
 
for(int col=0; col<matrix[0].length; col++){
 
System.out.print(matrix[row][col]);
if ( col < matrix[0].length-1 ) 
System.out.print(",");
 
}
System.out.println("");
}
 

[John Lockheart]

I've almost got it working, but i'm having difficulty with my coordinate system x and y. The way you wrote it matrix[y][x++] is the same way i did meaning x will always start from 1 not 0. It needs to start from 0,0 and proceed filling all the columns (if max column met, increase row and restart column). And if a string is encountered, skip it, and store a value in its place in the matrix. Or if the special case encountered, store that value n times.

[Mike Mc Afee]

Originally posted by John Lockheart:
I've almost got it working, but i'm having difficulty with my coordinate system x and y. The way you wrote it matrix[y][x++] is the same way i did meaning x will always start from 1 not 0. It needs to start from 0,0 and proceed filling all the columns (if max column met, increase row and restart column). And if a string is encountered, skip it, and store a value in its place in the matrix. Or if the special case encountered, store that value n times.

Since x++ would increment x after it's evaluated for matrix[y][x], I would have thought it would have stored at 0,0 and then x would be incremented to 1.

[John Lockheart]

I didn't realise that, that's good to know. I actually wrote it slightly diffrent so thats probably why I had a problem. Here's the code I have so far. When it runs into a string and since it's not storing it, it will decrease the index value (if y=#of columns decrease y, if y=0 reset y and decrease rows) x=rows, y=columns. I'm supposed to get the following output. Also if a string or special case(with strings) is encountered, i can't just skip ahead index values and store a null value so I have to decrease if that happens.

    
1 2 -3
4 -7 -7
-7 -7 -7
-7 8 9
11 0 0
 
I get:
1 2 -3
-7 -7 -7
11 -7 8
9 0 0
0 0 0
 
My coordinate system is flawed, replacing values etc...

    
import java.util.*;
import java.util.StringTokenizer;
import javax.swing.JOptionPane;
import java.io.*;
 
public class MatrixManipulation {
    public static void main(String[] args) {
 
    MatrixFill("a4q1.txt");
 
    }
 

public static void MatrixFill(String filename){
 
int rows = 0,
columns = 0,
x = 0,
y = 0,
int1,
int2;
 
int[][] matrix = null;
 
String line,
   token,
   token2;
 
boolean specialCase = false;
 
StringTokenizer tokenizer,
tokenizer2,
tokenizer3;
 
    BufferedReader input = null;
 
        try {
 
            input = new BufferedReader(new FileReader(filename));
line = input.readLine();
 
tokenizer = new StringTokenizer(line);
 
rows = Integer.parseInt(tokenizer.nextToken());
columns = Integer.parseInt(tokenizer.nextToken());
 
matrix = new int[rows][columns];
 
line = input.readLine(); //skip first line?
 
while (line != null && x<=matrix.length-1) {//process none blank lines
 
tokenizer2 = new StringTokenizer(line);
 
    while(tokenizer2.hasMoreTokens() == true) {//process tokens

 
    token = tokenizer2.nextToken();
 
       try{
matrix[x][y] = Integer.parseInt(token);
y++; //increase columns
 
if(y == matrix[0].length){//y=#of columns  y=0;  x++;
}
 

}catch (NumberFormatException e){//String caught (is it a special case?)
 
  for(int i=0; i<token.length()-1; i++){
 
if(token.charAt(i) == '*'){//search for special case "*"
            specialCase = true;
}
}

      if(specialCase == true){
 tokenizer3 = new StringTokenizer(token, "*");
 
     try{ //make sure special case has ints and not stringsint1 = Integer.parseInt(tokenizer3.nextToken()); //# of repetitionsint2 = Integer.parseInt(tokenizer3.nextToken()); //Integer to be stored
for(int i=0; i<int1; i++){
matrix[x][y] = int2; //assign integer to token (x many times)y++;//increase columns
if(y == matrix[0].length){//y=#of columns
y = 0;x++;}
}
 
}catch (NumberFormatException nfe){//special case had strings
JOptionPane.showMessageDialog(null, "Invalid Entry: " + token);
 
if(y == 0){//column index value is 0 
y=matrix[0].length-1;//set to max columns in matrix
x--;//decrease rows
}else{//decrease columns   y--;
}
 

}
   }else{ //wasn't special case, just a string     JOptionPane.showMessageDialog(null, "Invalid Entry: " + token);
 
}
 
     if(y == 0){
y=matrix[0].length-1;
x--;
    }else{
y--;
    }
 
}
}
 
line = input.readLine();
}
 
        } catch (FileNotFoundException e) {
            System.out.println("Unable to open file " + filename);
        } catch (IOException e) {
            System.out.println("Unable to read from file " + filename);
        }finally {
 
        // Close the file
        try {
           if (input != null)
           input.close();
        } catch (IOException e) {
           System.out.println("Unable to close file " + filename);
        }
 
     }
 
//print vector
for(int row=0; row<matrix.length; row++){
 
for(int col=0; col<matrix[0].length; col++){
 
System.out.println(matrix[row][col]);
 
}
}
 
    }
}
 

[John Lockheart]

sorry it's formatted so poorly, i didn't realise doing copy paste would do that...

[John Lockheart]

NEVERMIND. first time using try and catch statments, didn't realise there was absolutely no need to DECREASE columns and rows because it will try it, and if it catches it, columns and rows won't be increased in the first place. I'm sorry guys...at least i learned from my mistake (haha). Thanks for all the input though.

[Christophe Verré]

at least i learned from my mistake (haha)

That's the best way to learn

[Jim Yingst]

[John Lockheart]: sorry it's formatted so poorly, i didn't realise doing copy paste would do that...

For what it's worth, you can edit your own posts after you post them by clicking on the at the top of a given post.
[ February 28, 2007: Message edited by: Jim Yingst ]