Unit 5 sample programs

Preparing a Large File of Numbers
working with Tables and Files
Updating a Data File
Related Lists
Two-Dimensional Arrays
Locating the Largest number (finding WHERE it is)
Bubble Sort
Preparing a Large File for Searching
Seaching

Preparing a Large File of Numbers: Ass5s2p1.java

Write a program that will generate a list of n random numbers and saves it in a text file: The first line of the file will contain the number n. Let n be the number 1000, let the random numbers be integers between 1 and 100 (inclusive)


// The "Ass5s2p1" class.
import java.awt.*;
import java.io.*;
class Ass5s2p1
{
    static FileWriter f;
    static PrintWriter output;

    public static void main (String args []) throws IOException
    {
     f = new FileWriter ("a:rand1.txt");
     output = new PrintWriter (f);
     output.println (1000);
     for (int i = 0 ; i < 1000 ; i++)
     {
         int x = (int) (Math.random () * 100 + 1);
         output.println (x);
     }
     output.close ();
    } //end main
} //end Ass5s2p1

Illustrating working with Tables and Files Ass5s2p2.java

Write a program that will load the number file from 5.2.1 into an array of integers and that will let you enter a number between 1 and 100. It will then print out how often that number occurs in the file.


// The "Ass5s2p2" class.
import java.awt.*;
import java.io.*;
import hsa.Console;
class Ass5s2p2
{
    static Console cs;
    static int list [] = new int [1000];
    static int maxNum = 0;

    public static void main (String args []) throws IOException
    {
     cs = new Console ();
     loadTable ();
     cs.println ("Finding the Frequency of numbers in the Random File of 1000 numbers");
     cs.print ("Enter a number between 1 and 100 (enter 0 to end): ");
     int x = cs.readInt ();
     while (x != 0)
     {
         int t = howManyOf (x);
         cs.println("There are "+t+" occurrences of the number "+x);
         cs.print ("\nEnter a number between 1 and 100 (enter 0 to end): ");
         x = cs.readInt ();

     }
    } //end main


    public static void loadTable () throws IOException
    {
     FileReader f = new FileReader ("a:rand1.txt");
     BufferedReader input = new BufferedReader (f);
     String temp = input.readLine ();
     maxNum = Integer.parseInt (temp);
     for (int i = 0 ; i < maxNum ; i++)
     {
         temp = input.readLine ();
         list [i] = Integer.parseInt (temp);
     }
     input.close ();
    } //end loadTable


    public static int howManyOf (int ofThis)
    {
     int count = 0;
     for (int i = 0 ; i < maxNum ; i++)
         if (list [i] == ofThis)
          count++;
     return count;
    } //end howManyOf
} //end Ass5s2p2

Illustrating Updating a Data File: Ass5s2p4.java

Write methods void loadSet ( ); void saveSet ( ); void replaceOne (int newNum, int where) that will load the file from 5.2.1 into a global array of numbers; saves it again to the file; and replace the number in position "where" by the value of "newNum". Use these methods in a program that will let you change the value of the number in a specific location within the file.


// The "Ass5s2p4" class.
import java.awt.*;
import java.io.*;
import hsa.Console;
class Ass5s2p4
{
    static Console cs;
    static int list [] = new int [1000];
    static int maxNum = 0;

    public static void main (String args []) throws IOException
    {
     cs = new Console ();
     int where = 0, newVal = 0;
     loadSet ();
     cs.println ("Change the value of a number in a specific location");
     cs.println ("by picking a number between 1 and " + maxNum);
     cs.print ("Enter the location of the number you wish to change (0 to end):      ");
     where = cs.readInt ();
     while (where > 0 && where <= maxNum)
     {
         cs.print (" the value of that number is " + list [where] + ". Enter a new value: ");
         newVal = cs.readInt ();
         replaceOne (newVal, where);
         cs.print ("Enter the location of the number you wish to change (0 to end):      ");
         where = cs.readInt ();
     }
     saveSet ();
     cs.println ("bye");
    } //end main


    public static void loadSet () throws IOException
    {
     FileReader f = new FileReader ("a:rand1.txt");
     BufferedReader input = new BufferedReader (f);
     String temp = input.readLine ();
     maxNum = Integer.parseInt (temp);
     for (int i = 0 ; i < maxNum ; i++)
     {
         temp = input.readLine ();
         list [i] = Integer.parseInt (temp);
     }
     input.close ();
    } //end loadSet
    public static void saveSet () throws IOException
    {
     FileWriter f = new FileWriter ("a:rand1.txt");
     PrintWriter output = new PrintWriter (f);
     output.println (maxNum);
     for (int i = 0 ; i < maxNum ; i++)
         output.println (list [i]);
     output.close ();
    } //end saveSet



    public static void replaceOne (int newNum, int where)
    {
     if (where < maxNum && where >= 0)
         list [where] = newNum;
    } //end replaceOne
} //end Ass5s2p4

Illustrating RELATED LISTS: Ass5s3p1.java

Write a method void houseList( int listItem) that loads the titles of all 12 houses into the global String array house[12] and the apporpriate property into the global String array property[12]. For example houseList(2) would load the house names into house[12] and the personality discriptions into property[12]. Note that 1 stands for dates, 2 for personalities, 3 for colours, etc. Then write a program that will let you ask for an appropriate property, and list all 12 signs with that property. (Compare with problem 4.3.5)

// The "Ass5s3p1" class.
import java.awt.*;
import java.io.*;
import hsa.Console;
class Ass5s3p1
{
    static Console cs;
    static String houses [] = new String [12];
    static String properties [] = new String [12];

    public static void main (String args []) throws IOException
    {
	cs = new Console ();
	cs.println ("Each Zodiac sign has 7 qualities to save in a file:");
	cs.println ("               enter 1 for DATES");
	cs.println ("               enter 2 for PERSONALITY");
	cs.println ("               enter 3 for COLOURS");
	cs.println ("               enter 4 for PRECIOUS STONES");
	cs.println ("               enter 5 for METAL");
	cs.println ("               enter 6 for TREES");
	cs.println ("               enter 7 for FLOWERS");
	cs.println ("               enter 8 for PLANETARY RULER OF THE HOUSE");
	cs.print ("\nEnter a number between 1 to 8: ");
	int choice = cs.readInt ();
	if (choice > 0 && choice < 9)
	{
	    houseList (choice);
	    printList (cs);
	}
    } //end main


    public static void printList (Console c)
    {
	for (int i = 0 ; i < 12 ; i++)
	{
	    cs.clear ();
	    c.println ("the house of " + houses [i] + " exhibits: " + properties [i]);
	    c.print ("\npress ENTER to continue..");
	    char a = c.readChar ();
	    c.println ("\n");
	}
	c.println("you have reached the end");
    } //emd printList


    public static void houseList (int listItem) throws IOException
    {
	FileReader f = new FileReader ("a:zodiac.txt");
	BufferedReader input = new BufferedReader (f);
	String temp;
	for (int i = 0 ; i < 12 ; i++)
	{
	    houses [i] = input.readLine ();
	    for (int j = 1 ; j < listItem ; j++)
		temp = input.readLine ();
	    properties [i] = input.readLine ();
	    for (int j = listItem + 1 ; j < 9 ; j++)
		temp = input.readLine ();
	}
	input.close ();
    } //end houseList
} //end Ass5s3p1

Illustrating TWO DIMENSIONAL ARRAYS: Ass5s4p1.java

The Pascal triangle turned on its side looks as follows:

1    1    1    1    1    1    1     1     1     1  
1    2    3    4    5    6    7     8     9    10
1    3    6   10   15   21   28    36    45    55
1    4   10   20   35   56   84   120   165   220
1    5   15   35   70  126  210   330   495   715
1    6   21   56  126  252  462   792  1287  2002
1    7   28   84  210  462  924  1716  3003  5005
1    8   36  120  330  792 1716  3432  6435 11440
1    9   45  165  495 1287 3003  6435 12870 24310
1   10   55  220  715 2002 5005 11440 24310 48620

The first row are the numbers in p[0][0], p[0][1], p[0][2],..., p[0][9]
The familiar Pascal triangle is the triangle of numbers with p[0][0] as vertex and the set of numbers p[0][9], p[1][8], p[2][7], p[3][6], ..., p[9][0] as base.
Note that p[0][y] is always 1, and that any other number is obtained by adding two of its neighbours: the one above and the one to its left.
The number 15 for example is 5+10 (or 10+5, depending on which 15 you found) Write a program that will prints this array of numbers


// The "Ass5s4p1" class.
import java.awt.*;
import java.io.*;
import hsa.Console;
class Ass5s4p1
{
    static Console cs = new Console ();
    static int list [] [] = new int [10] [10];

    public static void main (String args []) throws IOException
    {
	//fill first row with 1
	for (int col = 0 ; col < 10 ; col++)
	    list [0] [col] = 1;
	//fill first column with 1
	for (int row = 1 ; row < 10 ; row++)
	    list [row] [0] = 1;
	//use the formula on the rest
	for (int col = 1 ; col < 10 ; col++)
	    for (int row = 1 ; row < 10 ; row++)
		list [row] [col] = list [row] [col - 1] + list [row - 1] [col];
	printList ();
    } //end main


    public static void printList ()
    {
	for (int col = 0 ; col < 10 ; col++)
	{
	    for (int row = 0 ; row < 10 ; row++)
		cs.print (list [row] [col], 7);
	    cs.println ("");
	}
    } //end printList
} //end Ass5s4p1

Illustrating LOCATING THE LARGEST : Ass5s5p4.java

Write a program that fills an array of 20 with a set of random integers between 10 and 99, prints out the list on one line, and underlines the two-digit largest number with the symbol "==".


// The "Ass5s5p4" class.
import java.awt.*;
import java.io.*;
import hsa.Console;
class Ass5s5p4
{
    static Console cs = new Console ();
    static int list [] = new int [20];

    public static void main (String args []) throws IOException
    {
	fillList ();
	for (int i = 0 ; i < 20 ; i++)
	    cs.print ("  " + list [i] + " ");
	int n = locate ();
	cs.println ("");
	for (int i = 0 ; i < n ; i++)
	    cs.print ("    ");
	cs.print (" ==  ");
    } //end main


    public static int locate ()
    {
	int largest = list [0];
	int location = 0;
	for (int i = 1 ; i < 20 ; i++)
	    if (largest < list [i])
	    {
		largest = list [i];
		location = i;
	    }
	return location;
    } // end locate


    public static void fillList ()
    {
	for (int i = 0 ; i < 20 ; i++)
	    list [i] = (int) (Math.random () * 90 + 10);
    } // end fillList
} //end Ass5s5p4

Illustrating BUBBLE SORT: Ass5s5p9.java

Write a program that uses the bubble sort to sort a set of random numbers.


/ The "Ass5s5p9" class.
import java.awt.*;
import java.io.*;
import hsa.Console;
class Ass5s5p9
{
    static final int max = 100;
    static Console cs = new Console ();
    static int list [] = new int [max];

    public static void main (String args []) throws IOException
    {
	fillList ();
	cs.println ("unsorted numbers:");
	printList ();
	bubbleSort ();
	cs.println ("sorted numbers:");
	printList ();
    } //end main


    public static void fillList ()
    {
	for (int i = 0 ; i < max ; i++)
	    list [i] = (int) (Math.random () * 1000 + 1);
    } //end fillList


    public static void swap (int a, int b)
    {
	int temp = list [a];
	list [a] = list [b];
	list [b] = temp;
    } //end swap


    public static void bubbleSort ()
    {
	boolean finished = false;
	while (!finished)
	{
	    finished = true;
	    for (int i = 1 ; i < max ; i++)
		if (list [i - 1] > list [i])
		{
		    swap (i - 1, i);
		    finished = false;
		}
	}
    } //end bubbleSort


    public static void printList ()
    {
	for (int i = 0 ; i < max ; i++)
	{
	    cs.print (list [i], 5);
	    if (i % 15 == 14)
		cs.println ("");
	}
	cs.println ("");
    } //end printList
} //end Ass5s5p9

Prepraring the Random.txt file for next program:

Generate a set of 1000 random numbers between 1 and 1000 and save the set in the text file: random.txt.


// The "Ass5s6p1prep" class.
import java.awt.*;
import java.io.*;
class Ass5s6p1prep
{
    static FileWriter f;
    static PrintWriter output;

    public static void main (String args []) throws IOException
    {
	f = new FileWriter ("a:random.txt");
	output = new PrintWriter (f);
	int number;
	//the first number is the total amount expected in the file
	 output.println (1000);
	for (int i = 0 ; i < 1000 ; i++)
	{
	    number = (int) (Math.random () * 1000 + 1);
	    output.println (number);
	}
	output.close ();
    } //end main
} //end Ass5s6p1prep

Illustrating SEARCHING: Ass5s6p1.java

Write a program that will first let you load the set of numbers into an array and secondly lets you enter a number for testing to see if that number is in the file. Use a method int positionOf(int number) that will return the position of the first occurence of "number" in the list of 1000. If the number is not there, then return the number -1.


// The "Ass5s6p1" class.
import java.awt.*;
import java.io.*;
import hsa.Console;
class Ass5s6p1
{
    static Console cs = new Console ();
    static int list [];
    static int max = 0;

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

	cs.print ("enter a number between 1 and 1000, to see if it is on file (0 to stop): ");
	int num = cs.readInt ();
	int loc = -1;
	while (num > 0 && num < 1001)
	{
	    loc = locationOf (num);
	    if (loc < 0)
		cs.println (num + " is not on file");
	    else
		cs.println (num + " is located at position " + loc);
	    cs.print ("enter a number between 1 and 1000, to see if it is on file (0 to stop): ");
	    num = cs.readInt ();
	}
    } //end main


    public static int locationOf (int num)
    {
	int location = -1;
	for (int i = 0 ; location < 0 && i < max ; i++)
	    if (list [i] == num)
		location = i;
	return location;
    } //end locationOf



    public static void loadList () throws IOException
    {
	FileReader f = new FileReader ("a:random.txt");
	BufferedReader input = new BufferedReader (f);
	String temp = input.readLine ();
	max = Integer.parseInt (temp);
	list = new int [max];
	for (int i = 0 ; i < max ; i++)
	    list [i] = Integer.parseInt (input.readLine ());
	input.close ();
    } // end loadList
} //end Ass5s6p1