Java Program

Kevo

Hi,
Im writing a program which makes a html page containing 25 images given by the user. The html code is read from 2 files(input1.txt and input2txt) and is written to the new html file. The problem is input1 is never written to the file. I think I am overwriting the file after I write input1 but I am not sure. Any ideas?

import java.io.*;
import java.util.*;
class Filepath
{
	public static void main(String[] args) 
	{
		String carrier1;
		String carrier2;
		System.out.println("Please enter the number images you are using:");
		int images = Console.readInt();
		int control = 1;
		System.out.println("Please enter the folder name:");
		String Foldername = Console.readString();
		try
		{
			PrintWriter webpage = new PrintWriter(new File(Foldername + ".html"));
			Scanner start = new Scanner(new File("input1.txt"));
			while (start.hasNextLine())
			{
				carrier1 = start.nextLine();
				System.out.print(carrier1);
				webpage.print(carrier1);
			}
		}
		catch (IOException e)
		{
		}
		try
		{
			PrintWriter webpage = new PrintWriter(new File(Foldername + ".html"));
			webpage.println("");
			webpage.println("");
			while (control <= images && control <= 25)
			{
				if (control < 10)
				{
					webpage.println("<a href='pics/" + Foldername + "/0" + control + ".jpg'><img src='pics/" + Foldername + "/thumbnails/0" + control + ".jpg' BORDER='0' width='100' height='100'></a>");
				}
				else
				{
					webpage.println("<a href='pics/" + Foldername + "/" + control + ".jpg'><img src='pics/" + Foldername + "/thumbnails/" + control + ".jpg' BORDER='0' width='100' height='100'></a>");
				}
				control++;
			}
			try
			{
				Scanner end = new Scanner(new File("input2.txt"));
				while (end.hasNext())
				{
					carrier2 = end.nextLine();
					webpage.print(carrier2);
				}
			}
			catch (IOException e)
			{
			}
			webpage.close();
		}
		catch (IOException e)
		{
		}
	}
}

pH

Yes most likely

Removed the 2nd

PrintWriter webpage = new PrintWriter(new File(Foldername + ".html"));

And put it all in a single try/catch block so that you still have scope of the initial webpage variable and it should work.

Dr Pepper

Agreed! Beat me to it pH

Also - Don't know if it makes a difference but you have used a method called hasNext() in the while loop which loops through 'end' but the method to loop through 'start' is called hasNextLine()

Kevo

Theres a similar problem with this code. It doesnt print anything at all. Although the file is still created. Can you see any problems?
Thanks for the quick replies.

import java.io.*;
import java.util.*;
class Filepath
{
	public static void main(String[] args) 
	{
		String carrier1;
		String carrier2;
		System.out.println("Please enter the number images you are using:");
		int images = Console.readInt();
		int control = 1;
		System.out.println("Please enter the folder name:");
		String Foldername = Console.readString();
		try
		{
			PrintWriter webpage = new PrintWriter(new File(Foldername + ".html"));
			Scanner start = new Scanner(new File("input1.txt"));
			while (start.hasNextLine())
			{
				carrier1 = start.nextLine();
				webpage.print(carrier1);
			}
			while (control <= images && control <= 25)
			{
				if (control < 10)
				{
					webpage.println("<a href='pics/" + Foldername + "/0" + control + ".jpg'><img src='pics/" + Foldername + "/thumbnails/0" + control + ".jpg' BORDER='0' width='100' height='100'></a>");
				}
				else
				{
					webpage.println("<a href='pics/" + Foldername + "/" + control + ".jpg'><img src='pics/" + Foldername + "/thumbnails/" + control + ".jpg' BORDER='0' width='100' height='100'></a>");
				}
				control++;
			}
			Scanner end = new Scanner(new File("input2.txt"));
			while (end.hasNextLine())
			{
				carrier2 = end.nextLine();
				webpage.print(carrier2);
				webpage.close();
			}
		}
		catch (IOException e)
		{
		}
	}
}

pH

Try replacing the webpage.println()'s with System.out.println().

or just set webpage = System.out;

run the program printing output to the screen, add additional debug prints to see where it's going - then when you're happy switch it back to the file.

Dr Pepper

webpage.close is inside the second while loop that loops through 'end' so the PrintWriter is being closed after the first iteration of this loop. Move it outside, after the while loop!

Dr Pepper

Also, you should have an 'e.printStackTrace()' in your catch statement so you will actually be notified of exceptions (instead of ignoring them!)

Kevo

It seems to skip everything after the first scanner is used.

Scanner start = new Scanner(new File("input1.txt"));

edit
Im getting a file not found exception on input1.txt. I dont understand why this is. input1.txt is in the same folder and the filenames match exactly.

pH

Dr Pepper wrote:

Also, you should have an 'e.printStackTrace()' in your catch statement so you will actually be notified of exceptions (instead of ignoring them!)

Agreed - Even better throw a RuntimeException - and use the thrown exception as the cause.

Never have empty catch blocks - your code may be taking an exception route and you don't know it

try {

...

} catch (Exception e) {
   throw new RuntimeException("Something bad happened", e);
}

Dr Pepper

Kevo wrote:

It seems to skip everything after the first scanner is used.

Scanner start = new Scanner(new File("input1.txt"));

edit
Im getting a file not found exception on input1.txt. I dont understand why this is. input1.txt is in the same folder and the filenames match exactly.

Not sure why this is myself.. Are you sure input1.txt is in the same folder as Filepath.java? You could try putting in the full path (e.g. "C:\\whatever\\input.txt"). I'm not familiar with the 'Scanner' object. Maybe the file input1.txt is open in another program and you cannot access it? (Although that probably wouldn't be a FNF exception)

smythmark

This may be your problem. As far as I know input1.txt doesn't have to be in the same folder as the .class file, but rather it needs to be in the folder that you run the program from. If this is already the case then buggered if I know.:D

Torak

smythmark wrote:

This may be your problem. As far as I know input1.txt doesn't have to be in the same folder as the .class file, but rather it needs to be in the folder that you run the program from. If this is already the case then buggered if I know.:D

Actually as far as i remember it has to be in the directory specified in the user.dir system property. (which defaults to the folder that you run from)

  System.out.println(System.getProperty("user.dir"));

Kevo

Torak wrote:

Actually as far as i remember it has to be in the directory specified in the user.dir system property. (which defaults to the folder that you run from)

  System.out.println(System.getProperty("user.dir"));

I used this code and input1.txt is definitely in the correct folder.
Heres the latest code:

import java.io.*;
import java.util.*;
class Filepath
{
	public static void main(String[] args) 
	{
		String carrier1;
		String carrier2;
		System.out.println("Please enter the number images you are using:");
		int images = Console.readInt();
		int control = 1;
		System.out.println("Please enter the folder name:");
		String Foldername = Console.readString();
		try
		{
			System.out.println("Begin");
			PrintWriter webpage = new PrintWriter(new File(Foldername + ".html"));
			System.out.println("Begin2");
			Scanner start = new Scanner(new File("input1.txt"));
			System.out.println("Begin3");
			while (start.hasNextLine())
			{
				System.out.println("1");
				carrier1 = start.nextLine();
				webpage.print(carrier1);
			}
			while (control <= images && control <= 25)
			{
				System.out.println("2");
				if (control < 10)
				{
					webpage.println("<a href='pics/" + Foldername + "/0" + control + ".jpg'><img src='pics/" + Foldername + "/thumbnails/0" + control + ".jpg' BORDER='0' width='100' height='100'></a>");
				}
				else
				{
					webpage.println("<a href='pics/" + Foldername + "/" + control + ".jpg'><img src='pics/" + Foldername + "/thumbnails/" + control + ".jpg' BORDER='0' width='100' height='100'></a>");
				}
				control++;
			}
			Scanner end = new Scanner(new File("input2.txt"));
			while (end.hasNextLine())
			{
				System.out.println("3");
				carrier2 = end.nextLine();
				webpage.print(carrier2);
			}
			webpage.close();
			System.out.println("End");
		}
		catch (IOException e)
		{
			throw new RuntimeException("Something bad happened", e);
		}
	}
}

pH

have you tried moving the input file to a known directory(c:\files) and opening it from there? If this works then you know where the problem is!

Scanner start = new Scanner(new File("C:\\files\\input1.txt"));

Also you could try this to see where java is looking for this file :

File f = new File("input1.txt");
System.out.println("File is [" + f.getAbsolutePath() + "]");
Scanner start = new Scanner( f );

Kevo

I can't believe this. I named the input file input1.txt.txt. It works perfectly now. Thanks for your help!

Just one more question. This is from a past paper.

Write a program which displays the maximum in a collection of integers passed as command line arguments. eg. java MaxInteger 4 7 6 3 8 9.

heres my attempt:

int max = 0;
int tmp;
int i = 0;
while (i < ?????????????????????????)
{
      tmp = args[i]
      if (tmp > max)
      {
             max = tmp;
      }
}
System.out.print(max);

I understand most of the questuion but i am unsure how to see the total amount of integers. Any ideas?
BTW this isn't homework.

Dr Pepper

The number of iterations for the loop is equal to args.length, therefor, instead of while use for(int i = 0; i < args.length; i++) Otherwise it looks good!

smythmark

Kevo wrote:

I can't believe this. I named the input file input1.txt.txt. It works perfectly now. Thanks for your help!
BTW this isn't homework.

You must have named it input1.txt and saved it as type text file. Very annoying feature of notepad:mad:

pH

smythmark wrote:

You must have named it input1.txt and saved it as type text file. Very annoying feature of notepad:mad:

Couple this with the brilliant idea that is 'hide extensions for known file types' ...