This class will implement a hash table. The hash table will hold data.pdf

This class will implement a hash table. The hash table will hold data items whose type is tuple.
This class will have following public methods and constructor. HashTable(int size) Finds the
smallest prime integer p whose value is at least size. Creates a hash table of size p where each
cell initially is NULL. It will determine the hash function to be used in the hash table by creating
the object new HashFunction(p). maxLoad () Returns the maximum load of the hash table
averageLoad () Returns the average load of the hash table size () returns the current size of the
hash table. numElements() returns the number of Tuples that are currently stored in the hash
table. loadFactor() return the load factor which is numElements()/size() add (Tuple t) Adds the
tuple t to the hash table; places t in the list pointed by the cell h(t.getKey()) where h is the hash
function that is being used. When the load factors become bigger than 0.7, then it
(approximately) doubles the size of the hash table and rehashes all the elements (tuples) to the
new hash table. The size of the new hash table must be: Smallest prime integer whose value is at
least twice the current size. search (int k) returns an array list of Tuples (in the hash table) whose
key equals k. If no such Tuples exist, returns an empty list. Note that the type of this method
must be ArrayList remove (Tuple t) Removes the Tuple t from the hash table.
Solution
HashTable.java
import java.math.BigInteger;
import java.util.ArrayList;
public class HashTable {
TupleCell[] hashTable; //Table to store Tuple cells
HashFunction hashFunction; //Current hash Function
public HashTable(int size) {
int actualSize = Math.abs(size);
while (!new BigInteger(Integer.toString(actualSize)).isProbablePrime(1))
actualSize++; //Determining next prime number
hashTable = new TupleCell[actualSize]; //Create tuple cells
hashFunction = new HashFunction(actualSize); //Create hash function
}
public int maxLoad() { //Maximum load in hash table
int maxValue = 0;
for (TupleCell tupleCell : hashTable) {
TupleCell node = tupleCell;
int count = 0;

while (node != null) {
count++;
node = node.nextCell;
}
if (count > maxValue) {
maxValue = count;
}
}
return maxValue;
}
public double averageLoad() { //avarage load in hash table
return ((double) numElements()) / size();
}
public int size() { //size of table
return hashTable.length;
}
public int numElements() { // number of elements in table
int count = 0;
for (TupleCell tupleCell : hashTable) {
count++;
}
}
return count;
}
public double loadFactor() { //load factor
return ((double) numElements()) / size();
}
public void add(Tuple t) {
TupleCell node = hashTable[hashFunction.hashIndex(t.getKey())];
if (node == null) {
hashTable[hashFunction.hashIndex(t.getKey())] = new TupleCell(t); //If hash table cell is
empty
} else {

while (node.nextCell != null) {
}
node.nextCell = new TupleCell(t); //adding new tuple to end of corresponding linked list
}
if (loadFactor() > 0.7) { //Rehash
int newSize = 2 * hashTable.length;
while (!new BigInteger(Integer.toString(newSize))
.isProbablePrime(1))
newSize++; //Finding next prime number
TupleCell[] newHashTable = new TupleCell[newSize];
HashFunction newHashFunction = new HashFunction(newSize);
rehash(newHashTable, newHashFunction); //Rehash based on new hashtable and new
hash function
hashTable = newHashTable;
hashFunction = newHashFunction;
}
}
private void rehash(TupleCell[] newHashTable, HashFunction newHashFunction) { //Rehash
funciton
for (TupleCell tupleCell : hashTable) { //iterating through each cell
while (node != null) { //iterating through each node in linked list
TupleCell reNode = newHashTable[newHashFunction
.hashIndex(node.t.getKey())];
if (reNode == null) {
newHashTable[newHashFunction.hashIndex(node.t.getKey())] = node; //Adding to
new hash table
} else {
while (reNode.nextCell != null) {
reNode = reNode.nextCell;
}
reNode.nextCell = node;
}
TupleCell temp = node;

temp.nextCell = null; //reseting next cell reference
}
}
}
public ArrayList search(int key) {
ArrayList returnList = new ArrayList();
TupleCell node = hashTable[hashFunction.hashIndex(key)]; //Getting corresponding linked
list
if (node.t.getKey() == key)
returnList.add(node.t); //match
}
return returnList;
}
public boolean remove(Tuple t) {
boolean found = false;
TupleCell node = hashTable[hashFunction.hashIndex(t.getKey())];
if (node != null) {
if (node.t.equals(t)) {
hashTable[hashFunction.hashIndex(t.getKey())] = node.nextCell; //if table cell
matches tuple
found = true;
} else {
TupleCell prevNode = node;
if (node.t.equals(t)) {
prevNode.nextCell = node.nextCell; //if node in linked list matches tuple
found = true;
break;
}
prevNode = node; //remove node
}
}
}

return found;
}
static class TupleCell { //Wrapper class for tuple with additional reference to next TupleCell -
for linked list
Tuple t;
TupleCell nextCell;
TupleCell(Tuple t) {
this.t = t;
}
}
}
class HashFunction { //Hash function class
int size;
public HashFunction(int p) {
this.size = p;
}
public int hashIndex(int key) { //key to index method
return Math.abs(key) % size;
}
}
Tuple.java
public class Tuple {
private int key;
public Tuple(int key){
this.key = key;
}
public int getKey() { //used by hash table
return key;
}
public String toString(){
return Integer.toString(key);
}
}

This class will implement a hash table. The hash table will hold data.pdf

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