Displaying characters in many ways.

[TampaTechGuy]

I am having trouble getting this going....

I am trying to:

1. System.out every other letter on the first line of my text file.
2. System.out (print out) every other line
3. and finally just characters at positions 26-53 of my last line.

Just an exercise I am working on to learn more about I/O files.

Here is my text file:

This is a basic test file to test out how
a file can be read into the super duper
application and how we can extract certain
characters at several different positions
to do whatever we need to with them.
This java program should be able to open a file
and print out every other letter on the first line;
and then print out every other line, and then finally
print characters 26-53 of this last line. I hope it has enough characters.

import java.io.*;
import java.util.*;

public class demo
{


public static void main(String args[])
{
String data = null;
int recCount = 0;

try
{
FileReader fr = new FileReader("C:\\Development\\demo.txt");
BufferedReader br = new BufferedReader(fr);
data = new String();

while ((data = br.readLine()) != null)
{
recCount++;
System.out.println(data);
}

}

catch (IOException e)
{
System.out.println("IOException error!");
e.printStackTrace();
}

}

}

[CaptainMorgan]

You might want to use charAt of the String class for numbers 1 and 3, and simple logic for number 2(reading every other line).

[roots]

Seems like homework for me but dont want to discourage you.

Code:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class demo {

	public static void main(String args[]) {
		String data = null;
		int recCount = 0;

		try {
			FileReader fr = new FileReader("C:\\Development\\demo.txt");
			BufferedReader br = new BufferedReader(fr);
			data = new String();

			// For the first line thing
			data = br.readLine();

			if (data != null) {
				char[] allCharacters = data.toCharArray();
				for (int i = 0; i < allCharacters.length; i++) {
					System.out.println(allCharacters[i]);
				}
			}
			
			
			// For other lines 
			while ((data = br.readLine()) != null) {
				recCount++; // What is this for ??
				System.out.println(data);
			}

			// This should help you with substring as well
			System.out.println(data.substring(26, 53));

		}

		catch (IOException e) {
			System.out.println("IOException error!");
			e.printStackTrace();
		}

	}

}

Hope it helps

[TampaTechGuy]

Like so...? sorry in advance about the formatting

public class demo
{

/**
* @param args
*/

;
public static void main(String args[])
{
String data = null;


try
{
FileReader fr = new FileReader("C:\\Development\\demo.txt");
BufferedReader br = new BufferedReader(fr);
data = new String();

while ((data = br.readLine()) != null)
{
System.out.println(data);
}

int len = data.length();

for (int j = 0; j < len; j = j + 2)
{
data.charAt(j);
System.out.println(j);
}

for (int j = 0; j < len; j = j + 2)
{
data.charAt(26);
System.out.println(j);
}



}

catch (IOException e)
{

System.out.println("IOException error!");
e.printStackTrace();
}


}

}

[TampaTechGuy]

kinda is like homework --- except no teacher to turn it in to!! ;-)

[CaptainMorgan]

Is there something wrong with both of your codes or am I doing something wrong? They compile, but when ran, end up outputing the text file verbatim and then crashing with a NullPointerException.

Tampa, try this one, albeit a bit naive, and I've left out the substring for you to figure out.

Code:

 import java.io.*;
import java.util.*;

public class demo { 
  public static void main(String args[]) {
    String data = null;
    int recCount = 0;

    try {
      FileReader fr = new FileReader("C:\\Development\\demo.txt");
      BufferedReader br = new BufferedReader(fr);
      data = new String();
      
      while ((data = br.readLine()) != null) {
        int length = data.length();
        for (int i = 0; i < length; i++) {
          System.out.print(data.charAt(i) + " ");
          i++;
        }
        System.out.println("");
        data = br.readLine(); // skips a line, which is 
                              //  naive, seek something better, but
                              //  you get the idea        
        recCount++;
      }

    } catch (IOException e) { 
      System.out.println("IOException error!");
      e.printStackTrace();
    }
  }
}

[roots]

Code:

for (int j = 25 ; j < 56 ; j = j + 2) // +2 thing .. ?? 
{
       char c = data.charAt(j);
       System.out.println(c);
}

You know where i made the changes ..

[TampaTechGuy]

Ok I will give that a shot Captain. Thanks for the help. First time I have ever used a forum... i usually just google stuff and put it all together.