import java.io.File;
import java.io.FileInputStream;
import java.io.PrintStream;
import java.io.FileNotFoundException;
import java.util.Scanner;

/** File.java - Experiment with opening, reading, and writing files.
 *  This is a simple empirical study of the file and memory systems.
 *  We are curious how long things take and how much space is occupied.
 *  In Java's System class there is a useful method called currentTimeMillis,
 *  which allows us to measure time to the nearest millisecond.
 */
public class Files
{
  public static void main(String [] args) throws FileNotFoundException
  {
    long t1 = System.currentTimeMillis();
    
    // Experiment #1:  Write a loop that creates 1000 empty files.
    // The files should be placed into a subfolder called dummy.
    // Let's call the files 1.txt thru 1000.txt.
    // To create a file, call the PrintStream constructor.  Then immediately
    // close the file, so that you are ready to create the next file.

    /******************* write your loop here ********************/
    
    long t2 = System.currentTimeMillis();
    long diff = t2 - t1;
    System.out.printf("File creations took %d ms.\n", diff);



    // Experiment #2:  Mwa-ha-ha-ha, time to delete!
    // Use the delete() method in the File class in the Java API.
    File dir = new File("dummy");
    File [] list = dir.listFiles();
    
    t1 = System.currentTimeMillis();
    
    /******************* write your loop here *******************/

    t2 = System.currentTimeMillis();
    diff = t2 - t1;
    System.out.printf("File deletions took %d ms.\n", diff);



    // Create one dummy file for the next experiment.
    PrintStream bigFile = new PrintStream("big.txt");
    t1 = System.currentTimeMillis();
    
    // Experiment #3:  Write 100 MB to one file.  How long will it take?
    // To reduce the loop overhead, write a loop with 1 million iterations.
    // On each iteration, write a 100-character string literal to the file.
    
    /******************** write your loop here *******************/
    
    t2 = System.currentTimeMillis();
    bigFile.close();

    diff = t2 - t1;
    System.out.printf("Writing 100 MB took %d ms.\n", diff);



    // Experiment #4:  Now, let's read the file.
    Scanner in = new Scanner(new FileInputStream("big.txt"));
    
    t1 = System.currentTimeMillis();
    
    /********************* write your loop here ******************/

    t2 = System.currentTimeMillis();
    in.close();
    
    diff = t2 - t1;
    System.out.printf("Reading 100 MB took %d ms.\n", diff);



    // Experiment #5:  Delete the big file.
    t1 = System.currentTimeMillis();
    File f = new File("big.txt");

    /**************** Tell Java to delete the file **************/

    t2 = System.currentTimeMillis();
    diff = t2 - t1;
    System.out.printf("Deleting a 100 MB file took %d ms.\n", diff);
  }
}