Tis annoying (java)

Kraken

ok here is the code.

import java.io.*;
public class hashtable
{
  static int [ ] table; 	//  hash table array
  static int divisor;			//  hash function divisor


	public static void main(String[] args) throws Exception
	{
  BufferedReader kbd = new BufferedReader(new InputStreamReader (System.in));

	int eventType;
  int num = 0;
  int j;
  int i;
  int HashEntry;
  int size;			//  number of elements in table
  int index;

        System.out.println("Program working correctly");
 System.out.println("\n\nHow many buckets do you want in the hash table?\n enter number of buckets must be between 5 and 15: ");
 divisor =     Integer.parseInt (kbd.readLine());
           table = new int [divisor];
           do {
  System.out.println("..................................");
	System.out.println("Enter your option ");
	System.out.println("1. Add integer ");
	System.out.println("2. Remove integer ");
	System.out.println("3. Search for integer ");
  System.out.println("4. Exit ");
  System.out.println("..................................");

	eventType = Integer.parseInt (kbd.readLine());

	switch(eventType)
	   {

	  case 1:
		System.out.println("The number you want to add is?\n please eneter number");
    num = Integer.parseInt (kbd.readLine());
    put(num);
               display();
		break;
	   case 2:
		System.out.println("Which integer are you searching for\n\n enter the integer to begin search ");
    num = Integer.parseInt (kbd.readLine());
    index = get(num);

		break;
    case 3:
		System.out.println("select integer to be removed ");
      num = Integer.parseInt (kbd.readLine());

      display();
		break;

    
    case 4:

     break;
	   default:
		System.out.println("Invalid selection ");
	}      //  end of switch
  }
  while ( num != 4);
}  //  end of main method
////////////////////////////////////////////////////////////////////////////////
              //  method put
public static void put(int theKey)
{
	//search the table for a matching element
	int b = search(theKey);

	//  check if matching element found
	if (table[b] == 0)
	{
		//  no matching element and table is not full
		table [b] = theKey;
	}
	else
  {
		 	throw new IllegalArgumentException("table is full");
  }
} //  end of put
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
//  Display the array contents

   public static void display()  {



      for(int j=0; j<divisor; j++)           // for each element,
         System.out.print(table[j] + "  ");   // display it
      System.out.println("");
   }  //  end display method
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
    //  method search
private static int search(int theKey)
{
	int i = (theKey) % divisor;  	// home bucket
	int j = i;					// start at home
	do
	{
		if (table[j] == 0 || table[j] == theKey)
			return j;
		j = (j+1) % divisor;		//  next bucket
	} while (j!= i);			//  returned to home bucket
	return j;				// table full
}
////////////////////////////////////////////////////////////////////////////////


////////////////////////////////////////////////////////////////////////////////
//  method get
public static int get(int theKey)
{
	//search the table
	int b = search(theKey);

	//  see if a match was found at table [b]
	if (table[b] == 0 || table[b] != theKey)
		return -1;			//  no match

	return b;		//  matching element
}

}
////////////////////////////////////////////////////////////////////////////////

 //  end of class

problem it wont work properly and i know i have some stuff spelt wrong but only in print out lines? any ideas lads help would be nice after me work still have to add some stuff to it like if int != 5 or 15 for it to say no u bitch wrong number.

Enygma

First off your menu is wrong Remove and Search are mixed up. Only a little thing.

Not sure what you mean by it's not working either because it does run, everything else is just symantics.

The add works just fine, but the remove is just a 'get' it doesn't actually remove the number. Write a method called remove(int n) that just sets table[n] to 0.

Your search seems to be ok too, didn't take much of a look at it.

For case 4 just call System.exit(0);
That will quit the program, watch out though, if someone enters four at any time the program will exit. That's because the loop is while (num != 4)


Another thing, usually a put in a hashtable returns the value it is replacing, if it is replacing something. Can be useful.

Kraken

Yeah i coped the messed up in remove and search.
as for it working well the case 4 thing is ****ed up.
the remove wasent working. have fixed some of these errors. but still not right. oh wel have to plough on like a big farmer i guess.

Enygma

Why not use case 0 to exit? Or 999 or something that no one would be typing in for the duration of the application.

Kraken

while ( eventType != 4);

simple syntax error worked the other way but now at least it wont exit every time u enter 4.

remove wont work here ill post the new code. still unfinished

import java.io.*;
public class hashtable
{
  static int [ ] table; 	//  hash table array
  static int divisor;			//  hash function divisor


	public static void main(String[] args) throws Exception
	{
  BufferedReader kbd = new BufferedReader(new InputStreamReader (System.in));

	int eventType;
  int num = 0;
  int j;
  int i;
  int HashEntry;
  int size;			//  number of elements in table
  int index;

        System.out.println("Program working correctly");
 System.out.println("\n\nHow many buckets do you want in the hash table?\n enter number of buckets must be between 5 and 15: ");
 divisor =     Integer.parseInt (kbd.readLine());
           table = new int [divisor];
           do {
  System.out.println("..................................");
	System.out.println("Enter your option ");
	System.out.println("1. Add integer ");
	System.out.println("2. Remove integer ");
	System.out.println("3. Search for integer ");
  System.out.println("4. Exit ");
  System.out.println("..................................");

	eventType = Integer.parseInt (kbd.readLine());

	switch(eventType)
	   {

	  case 1:
		System.out.println("The number you want to add is?\n please enter number");
    num = Integer.parseInt (kbd.readLine());
    put(num);
               display();
		break;
	   case 2:
		System.out.println("Which integer are you want to remove\n\n enter the integer to begin search ");
    num = Integer.parseInt (kbd.readLine());
             display();

		break;
    case 3:
		System.out.println("select integer to be searched for \n\n enter the integer to begin search ");
          num = Integer.parseInt (kbd.readLine());
             index = get(num);
                 if (index == -1)
                 System.out.println("Key not found");
                 else
		break;


    case 4:

     break;
	   default:
		System.out.println("Invalid selection ");
	}      //  end of switch
  }
  while ( eventType != 4);
}  //  end of main method
////////////////////////////////////////////////////////////////////////////////
              //  method put
public static void put(int theKey)
{
	//search the table for a matching element
	int b = search(theKey);

	//  check if matching element found
	if (table[b] == 0)
	{
		//  no matching element and table is not full
		table [b] = theKey;
	}
	else
  {
		 	throw new IllegalArgumentException("table is full");
  }
} //  end of put
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
//  Display the array contents

   public static void display()  {



      for(int j=0; j<divisor; j++)           // for each element,
         System.out.print(table[j] + "  ");   // display it
      System.out.println("");
   }  //  end display method
////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////
    //  method search
private static int search(int theKey)
{
	int i = (theKey) % divisor;  	// home bucket
	int j = i;					// start at home
	do
	{
		if (table[j] == 0 || table[j] == theKey)
			return j;
		j = (j+1) % divisor;		//  next bucket
	} while (j!= i);			//  returned to home bucket
	return j;				// table full
}
////////////////////////////////////////////////////////////////////////////////


////////////////////////////////////////////////////////////////////////////////
//  method get
public static int get(int theKey)
{
	//search the table
	int b = search(theKey);

	//  see if a match was found at table [b]
	if (table[b] == 0 || table[b] != theKey)
		return -1;			//  no match

	return b;		//  matching element
}

}
////////////////////////////////////////////////////////////////////////////////

 //  end of class

if u could post the correct code for the areas it would be great.

System.out.println("select integer to be searched for \n\n enter the integer to begin search ");
          num = Integer.parseInt (kbd.readLine());
             index = get(num);
                 if (index == -1)// this here is only the start of a bigger piece cant rember off hand why but think it is supposed to say something like if thekey u entered is != to any key in table print not found else print thekey +position just cant figure out how exactly to do that.YET
                 System.out.println("Key not found");
                 else
		break;

Enygma

OK your put should be something like this:
[PHP]
public static int put(int key, int value) throws IllegalArgumentException
{
int previousValue = 0;
if (key > table.size)
{
throw new IllegalArgumentException("Key too big");
}
else
{
int previousValue = table[key];
table[key] = value;
}
return previousValue;
}
[/PHP]
This just checks to see if the key (index) will fit in the table. If it's ok it will store the previous value (so it can be returned) and sets the new value.

Your search method would be something like this:
[PHP]
public static int search (int key) throws IllegalArgumentException
{
int returnValue = 0;
if (key > table.size)
{
throw new IllegalArgumentException("Key too big");
}
else
{
returnValue = table[key];
}
return returnValue;
}

.
.
.
// use it like this
try
{
if (search(key) >= 1)
{
// on the premise that no one's going to 'put' a value of 0
System.out.println("Found it");
}
}
catch (IllegalArgumentException iae)
{
// whatever
}
[/PHP]

Your remove should be simple enough:
[PHP]
public static int remove(int key) throws IllegalArgumentException

{
int previousValue = 0;
if (key > table.size)
{
throw new IllegalArgumentException("Key too big");
}
else
{
previousValue = table[key];
table[key] = 0;
}
return previousValue;
}
[/PHP]

Hope this helps.

Kraken

Cheers mate will try it out now.
Looks good. understand it all which is even better. dont know why it did not dawn on me to try it b4.

cheers again