1. ./DataIODemo.java
2. ./FileTest.java
3. ./InvoiceUsingText.java

package examples;

import java.io.*;

/**
 * Demonstrate use of DataInput/OutputStreams with merchandise invoices.
 * 
 */
public class DataIODemo {

	/**
	 * 
	 * @param args
	 *            - not used in this program
	 * @throws IOException
	 */
	public static void main(String[] args) throws IOException {

		// I know I don't want this variable to change within this method, so
		// made it final
		final String FILENAME = "invoice.dat";

		// stream to write the data out
		DataOutputStream out = new DataOutputStream(new FileOutputStream(
				FILENAME));

		double[] prices = { 19.99, 9.99, 15.99, 3.99, 4.99 };
		int[] units = { 12, 8, 13, 29, 50 };
		String[] descs = { "Java T-shirt", "Java Mug", "Java Beach Towel",
				"Java Pin", "Java Key Chain" };

		// write the data out
		for (int i = 0; i < prices.length; i++) {
			out.writeDouble(prices[i]);
			out.writeChar('\t');
			out.writeInt(units[i]);
			out.writeChar('\t');
			out.writeChars(descs[i]);
			out.writeChar('\n');
		}
		out.close();

		// read the data in again
		DataInputStream in = new DataInputStream(new FileInputStream(FILENAME));

		double price;
		int unit;
		StringBuilder desc;
		double total = 0.0;

		final String lineSepString = System.getProperty("line.separator");
		char lineSep = lineSepString.charAt(0);

		while (in.available() > 0) {
			price = in.readDouble();
			in.readChar(); // throws out the tab
			unit = in.readInt();
			in.readChar(); // throws out the tab
			char chr;
			desc = new StringBuilder(20);
			while ((chr = in.readChar()) != lineSep)
				desc.append(chr);
			System.out.println("You've ordered " + unit + " units of " + desc
					+ " at $" + price);

			total = total + unit * price;
		}
		in.close();

		// 2 ways to do the same thing:
		System.out.printf("For a TOTAL of $%.2f\n", total);
		// OR
		System.out.format("For a TOTAL of $%.2f", total);
	}
}

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

/**
 * Demonstrate using File objects and FileInputStreams in Java.
 * 
 * @author Sara Sprenkle
 * 
 */
public class FileTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// String basedir =
		// "/Users/sprenkle/Documents/WLU/CS209/fall2015/workspace/11-exceptions_streams";
		String basedir = ".";
		// create a file that represents the current directory
		// File f = new File(basedir + File.separator + "chicken.data");
		File f = new File("chicken.data");
		System.out.println("File is " + f.getAbsolutePath());
		try {
			
			FileInputStream fin = new FileInputStream(f);
			while (fin.available() > 0) {
				System.out.println(fin.read());
			}
			
			/* Consider how we'd write the code if we don't use the available() method:
			 * When would the loop stop?
			 * The loop would keep going, waiting for more input.  That could be valid code,
			 * but more often, you probably want to stop looping when you run out of stuff to read,
			 * like from a file.
			 */
			/*
			while( true ) {
				int input = fin.read();
				System.out.println(input);
			}
			*/
			fin.close();
			
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}

		File notAFile = new File("/this/is/not/a/file");
		displayInfo(f);
		displayInfo(notAFile);

	}

	/**
	 * Displays info about the file
	 * @param myFile
	 */
	private static void displayInfo(File myFile) {
		System.out.println(myFile.getAbsolutePath() + " is a file: "
				+ myFile.isFile());
		System.out.println(myFile.getAbsolutePath() + " is a directory: "
				+ myFile.isDirectory());
	}

}

package examples;

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

/**
 * Demonstrate use of PrintWriter/Scanner with merchandise invoices.
 * 
 */
public class InvoiceUsingText {

	public static void main(String[] args) throws IOException {

		final String FILENAME = "invoice.dat";

		writeInvoiceToFile(FILENAME);

		// read it in again
		Scanner in = new Scanner(new FileReader(FILENAME));

		double price;
		int unit;
		String desc;
		double total = 0.0;

		while (in.hasNext()) {
			price = in.nextDouble();
			unit = in.nextInt();
			in.skip("\t"); // eat tab
			desc = in.nextLine();
			System.out.println("You've ordered " + unit + " units of " + desc
					+ " at $" + price);
			total = total + unit * price;
		}
		in.close();

		// 1.5+ way
		System.out.printf("For a TOTAL of $%10.2f\n", total);
		// OR
		System.out.format("For a TOTAL of $%.2f", total);
	}

	/**
	 * @param filename
	 * @throws FileNotFoundException
	 */
	public static void writeInvoiceToFile(final String filename)
			throws FileNotFoundException {
		// write the data out
		PrintWriter out = new PrintWriter(filename);

		double[] prices = { 19.99, 9.99, 15.99, 3.99, 4.99 };
		int[] units = { 12, 8, 13, 29, 50 };
		String[] descriptions = { "Java T-shirt", "Java Mug", "Java Beach Towel",
				"Java Pin", "Java Key Chain" };

		for (int i = 0; i < prices.length; i++) {
			out.print(prices[i]);
			out.print('\t');
			out.print(units[i]);
			out.print('\t');
			out.println(descriptions[i]);
		}
		out.close();
	}
}