// File Demo
// (c) 1999 Andrea Danyluk

import java.io.*;  // need this in order to do file io.

public class FileDemo
{

// pre: fileName is a valid file name
// post: writes the integers 0 - 20 to a file
public static void writeToFile(String fileName) throws IOException
{
	DataOutputStream outFile = new DataOutputStream(new FileOutputStream(fileName));
	for (int i = 0; i <= 20; i++)
		outFile.writeInt(i);
	outFile.writeInt(-100);		// mark the end of the file
	outFile.close();
}

// pre: filename is a valid file name
// post: returns a vector containing numbers read from the file
public static int[] readFromFile(String fileName) throws IOException
{
	int[] numbers = new int[21];
	int temp = 0;
	int index = 0;
	DataInputStream inFile = new DataInputStream(new FileInputStream(fileName));
	temp = inFile.readInt();
	
	while (temp != -100)
	{
		numbers[index] = temp;
		index++;
		temp = inFile.readInt();
	}
	inFile.close();
	return numbers;
}

	public static void main(String args[])
	{
		System.out.println( "Here we go..." );
		String myFileName = "NumbersFile";
		
		try			// all file operations must be within "try"
		{
			writeToFile(myFileName);
		}

		catch(IOException e)	// error with file operation
		{
			System.out.println("File error on output!\n"+ e.toString());
		}
		
		try
		{
			int[] someNumbers = readFromFile("bob");
			for (int i = 0; i < someNumbers.length; i++)
				System.out.println(someNumbers[i]);
		}
		catch (FileNotFoundException e)
		{
			System.out.println("File not found for read.");
		}
		catch(IOException e)	// generic error with file operation
		{
			System.out.println("File error on input!\n"+ e.toString());
		}
		
		System.out.println("But we can still go on!");
	}
}