9 replies to this topic

[TCooney]

Hi There, I am a college student and need some help with an assignment I am working on.

I have to create a hash table using linear probing that will allow to search the state capitals of the united states. If you could, please look at my code and see where I am going wrong!

import java.io.*;

import java.util.Scanner;


public class CapitalsTable {

    private CapitalsHash[] capitalArray;

    private int arraySize;

    private CapitalsHash nonCapital;


    public CapitalsTable(int size)

    {

        arraySize=size;

        capitalArray = new CapitalsHash[arraySize];

        nonCapital = new CapitalsHash(-1);

    }


    public void displayTable()

    {

        System.out.print("Table:");

        for (int j=0;j<arraySize;j++)

        {

            if(capitalArray[j] !=null)

                    System.out.print(capitalArray[j].getKey() + " ");

            else

                System.out.print("**");


            }

        System.out.println("");

        }

    public static int hashFunc(String key)

            {

        int hashVal=0;

        for(int j=0;j<key.length();j++)

            {

            hashVal=(127*hashVal+key.charAt(j))

                    %75;

            }

        return hashVal;

    }

    public void insert(CapitalsHash state)

    {

        int key = state.getKey();

        int hashVal = hashFunc(key);


        while(capitalArray[hashVal] !=null &&

                capitalArray[hashVal].getKey() !=-1)

        {

            ++hashVal;

            hashVal %=arraySize;

        }

        capitalArray[hashVal] = state;

    }

    public CapitalsHash delete(int key)

    {

        int hashVal = hashFunc(key);


        while (capitalArray[hashVal] !=null)

        {

            if(capitalArray[hashVal].getKey() == key)

            {

                CapitalsHash temp = capitalArray[hashVal];

                capitalArray[hashVal] = nonCapital;

                return temp;

            }

          ++hashVal;

          hashVal %=arraySize;

        }

        return null;

    }

    public CapitalsHash find(int key)

    {

        int hashVal = hashFunc(key);


        while (capitalArray[hashVal] !=null)

        {

            if(capitalArray[hashVal].getKey() == key)

                return capitalArray[hashVal];

            ++hashVal;

            hashVal %=arraySize;

        }

         return null;

    }

}

In my insert, delete, and find functions, netbeans keeps telling me that "key" is not an integer. please help!

[WingedPanther]

in HashFunc, you passed key as a string.

[TCooney]

Because the Key is a string, I am inputing a state name

[WingedPanther]

Which line is it complaining about?

[Xylyze]

Can you show the code for the class CapitalsHash?

Also, at line 42:

int hashVal = hashFunc(key);

You pass an int but hashFunc expects a String.

[TCooney]

public class CapitalsHash {
    private int Capitals;

    public CapitalsHash(int ii)
    {
        Capitals=ii;
    }
    public int getKey()
    {
        return Capitals;
    }
}

It's complaining about

int hashVal = hashFunc(key);

[TCooney]

If you guys think I'm going the wrong way about, please feel free to let me know what you think might work better

[Xylyze]

If you use:

int hashVal = hashFunc(key+"");

instead of:

int hashVal = hashFunc(key);

your code will compile atleast. But I'm not sure if it's going to do what you want it to do. (if that made any sense)

[Xylyze]

TCooney said:

If you guys think I'm going the wrong way about, please feel free to let me know what you think might work better

Well for starters, the CapitalsHash class is a wrapper class for just one int. In the constructor you set the value and with the getKey method you get the value. So in my opinion the whole class is redundant. You can always use Integer if you don't want to work with the primitive int.

[TCooney]

Well it did take away the errors, I'll see if I can get it to work now and let you guys know