1. ./ClosingStreams.java
2. ./ConsoleUsingConsoleDemo.java
3. ./ConsoleUsingScannerDemo.java
4. ./DataIODemo.java
5. ./FileTest.java
6. ./ScannerPreventExceptions.java
7. ./SystemIOExample.java
8. ./SystemIOInClass.java
9. ./SystemIOReaderExample.java
10. ./SystemIOReaderInClass.java
11. ./SystemIOReaderStarter.java
12. ./SystemIOStarter.java

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Demonstrates what happens when you close the outermost connected stream.
 * 
 * @author Sara Sprenkle
 */
public class ClosingStreams {

	public static void main(String[] args) {
		try {
			FileInputStream fis = new FileInputStream("myfile.dat");

			BufferedReader br = new BufferedReader(new InputStreamReader(fis));
			br.close();

			// calling a reading-related method on the fis stream will throw an exception
			// because the stream is already closed.
			fis.available();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

/**
 * 
 */
package examples;

import java.io.Console;

/**
 * A program that demonstrates reading in from the console, using calculating
 * the area of a rectangle as the example.
 * 
 * Does not work within an IDE directly--have to run from a terminal.
 * 
 * Note that this class does not have the error checking that
 * ConsoleUsingScannerDemo has.
 * 
 * @author Sara Sprenkle
 */
public class ConsoleUsingConsoleDemo {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		System.out
				.println("This program calculates the area of a rectangle.\n");

		Console console = System.console();
		if (console == null) {
			System.err.println("No console.");
			System.exit(1);
		}

		// prompt the user for the width
		String widthPrompt = "Please enter the width of a rectangle (as an integer): ";

		// check for bad input, read in the integer representing the width
		String widthLine = console.readLine(widthPrompt);

		int width = Integer.parseInt(widthLine);

		// prompt the user for the height
		String heightPrompt = "Please enter the height of a rectangle (as an integer): ";

		// check for bad input, read in the integer representing the width
		String heightLine = console.readLine(heightPrompt);

		int height = Integer.parseInt(heightLine);
		int area = height * width;

		System.out.println("The area of your rectangle is " + area + ".");
	}

}

package examples;

import java.util.Scanner;

/**
 * A program that demonstrates reading in from the console, using calculating
 * the area of a rectangle as the example.
 * 
 * @author Sara Sprenkle
 */
public class ConsoleUsingScannerDemo {

	/**
	 * @param args
	 *            not used in this program
	 */
	public static void main(String[] args) {
		System.out
				.println("This program calculates the area of a rectangle.\n");

		// open the Scanner on the console input, System.in
		Scanner scan = new Scanner(System.in);

		// Comment this out and enter the text "6 7", for example
		scan.useDelimiter("\n"); // breaks up by lines, useful for
									// console I/O

		// prompt the user for the width
		String widthPrompt = "Please enter the width of a rectangle (as an integer): ";

		promptAndHandleIntegerInput(scan, widthPrompt);

		int width = scan.nextInt();
		scan.nextLine(); // eat the new line that the user entered after the
							// width was entered (why is there another new
							// line?)

		// prompt the user for the height
		String heightPrompt = "Please enter the height of a rectangle (as an integer): ";
		promptAndHandleIntegerInput(scan, heightPrompt);
		int length = scan.nextInt();
		// don't need to worry about eating the new line because not getting any
		// more user input after this.
		scan.close();

		int area = length * width;

		System.out.println("The area of your rectangle is " + area + ".");
	}

	/**
	 * Handles prompting for integer input and verifying that we get an integer
	 * back.
	 * 
	 * @param scan
	 * @param prompt
	 *            the prompt used to request the input
	 */
	private static void promptAndHandleIntegerInput(Scanner scan, String prompt) {
		System.out.print(prompt);

		// check for bad input, read in the integer representing the width
		while (!scan.hasNextInt()) {
			handleBadInput(scan, prompt);
		}
	}

	/**
	 * When the user enters bad input, remove the rest of what's on the line
	 * from the scanner and print out an error message and a reminder of what
	 * the input should look like.
	 * 
	 * @param scan
	 *            where the bad input is coming from
	 * @param prompt
	 *            a reminder of what we're looking for
	 */
	public static void handleBadInput(Scanner scan, String prompt) {
		// read the bad input (up to the \n, which is what the user
		// entered to trigger reading the input)
		if (scan.hasNextLine()) {
			scan.nextLine();
		}

		// give an error message and then repeat what we want
		System.out.println("Incorrect input.");
		System.out.print(prompt);
	}

}

import java.io.*;

/**
 * Demonstrate use of DataInput/OutputStreams with merchandise invoices.
 * 
 * @author CSCI209
 */
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; file will contain bytes because it's an OutputStream
		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 CSCI209
 * 
 */
public class FileTest {

	// Can easily change the base directory: 
	private static final String BASE_DIR = ".";

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		//~~~~  create a few different files:   ~~~~
		File baseDir = new File(BASE_DIR);
		File notAFile = new File("/this/is/not/a/file");
		// create a file that represents a file in the current directory
		// in 3 different ways: 
		File f = new File("chicken.data"); // default is current directory
		File f2 = new File(baseDir + File.separator + "chicken.data");
		File f3 = new File(baseDir, "chicken.data");

		System.out.println("Reading file: " + 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();
		}

		displayInfo(baseDir);
		displayInfo(f);
		displayInfo(f2);
		displayInfo(f3);
		displayInfo(notAFile);

	}

	/**
	 * Displays info (if it's a file and if it's a directory) about the given file
	 * 
	 * @param myFile the file to display information about
	 */
	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.util.Scanner;

public class ScannerPreventExceptions {
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		System.out.print("Enter a long: ");
		
		while( ! sc.hasNextLong() ) {
			System.out.println("Oops, that's not a long.");
			System.out.println("Please try again...");
			// read in what they incorrectly entered
			sc.nextLine(); 
			System.out.print("Enter a long: ");
		}

		long myLong = sc.nextLong();
		
		System.out.println("You entered " + myLong);
		sc.close();
	}

}

import java.io.IOException;

/**
 * Demonstrating some use of the System.in and System.out objects
 * 
 * @author CSCI209
 *
 */
public class SystemIOExample {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		System.out.println("Trying out System.out and System.in classes");
		
		System.out.print("Enter an integer: ");
		int number = 0;
		try {
			number = System.in.read();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println("User did not enter a number?");
		}
		
		System.out.println("You entered " + number);
	}

}

import java.io.IOException;

/**
 * Demonstrating some use of the System.in and System.out objects
 * 
 * @author CSCI209
 *
 */
public class SystemIOInClass {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		System.out.println("Trying out System.out and System.in classes");
		
		System.out.print("Enter an integer: ");
		int number = 0;
		try {
			number = System.in.read();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		System.out.println("You entered " + number);
	}

}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 * Demonstrating some use of the System.in and System.out objects
 * with the BufferedReader class
 * 
 * @author CSCI209
 *
 */
public class SystemIOReaderExample {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		System.out.println("Trying out System.out and System.in classes, using a BufferedReader");
		
		System.out.print("Enter an integer: ");
		
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		
		int number=0;
		try {
			String line = in.readLine();
			number = Integer.valueOf(line);
			in.close();
		} catch (IOException e) {
			e.printStackTrace();
			// This is a failure -- should exit gracefully.
			System.exit(0);
		}
		
		System.out.println("You entered " + number);
		
	}

}

import java.io.IOException;

/**
 * Demonstrating some use of the System.in and System.out objects with the
 * BufferedReader class
 * 
 * @author CSCI209
 *
 */
public class SystemIOReaderInClass {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		System.out.println("Trying out System.out and System.in classes, using a BufferedReader");

		System.out.print("Enter an integer: ");

		int number = 0;
		try {
			number = System.in.read();
		} catch (IOException e) {
			e.printStackTrace();
			// This is a failure -- should exit gracefully.
			System.exit(0);
		}

		System.out.println("You entered " + number);

	}

}

import java.io.IOException;

/**
 * Demonstrating some use of the System.in and System.out objects with the
 * BufferedReader class
 * 
 * @author CSCI209
 *
 */
public class SystemIOReaderStarter {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		System.out.println("Trying out System.out and System.in classes, using a BufferedReader");

		System.out.print("Enter an integer: ");

		int number = 0;
		try {
			number = System.in.read();
		} catch (IOException e) {
			e.printStackTrace();
			// This is a failure -- should exit gracefully.
			System.exit(0);
		}

		System.out.println("You entered " + number);

	}

}

/**
 * Demonstrating some use of the System.in and System.out objects.
 * Needs to be updated to handle checked exception.
 * 
 * @author CSCI209
 *
 */
public class SystemIOStarter {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		System.out.println("Trying out System.out and System.in classes");
		
		System.out.print("Enter an integer: ");
		int number = System.in.read();
		
		System.out.println("You entered " + number);
	}

}