import java.io.IOException;
public class HashTable {
private DataItem[] hashArray;
private int arraySize;
private DataItem bufItem; // for deleted items
public HashTable(int size) {
arraySize = size;
hashArray = new DataItem[arraySize];
bufItem = new DataItem(-1); // deleted item key is -1
}
public void displayTable() {
System.out.print("Table: ");
for (int j = 0; j < arraySize; j++) {
if (hashArray[j] != null)
System.out.print(hashArray[j].getKey() + " ");
else
System.out.print("#");
}
System.out.println("");
}
public int hashFunction(int key) {
return key % arraySize;
}
public void insert(DataItem item){
int key = item.getKey();
int hashVal = hashFunction(key); // hash the key
// until empty cell or -1,
while (hashArray[hashVal] != null && hashArray[hashVal].getKey() != -1) {
++hashVal; // go to next cell
hashVal %= arraySize; // wraparound if necessary
}
hashArray[hashVal] = item; // insert item
}
public DataItem delete(int key) {
int hashVal = hashFunction(key);
while (hashArray[hashVal] != null) // until empty cell,
{
if (hashArray[hashVal].getKey() == key) {
DataItem temp = hashArray[hashVal]; // save item
hashArray[hashVal] = bufItem; // delete item
return temp;
}
++hashVal; // go to next cell
hashVal %= arraySize; // wraparound if necessary
}
return null; // can't find item
}
public DataItem find(int key) // find item with key
{
int hashVal = hashFunction(key); // hash the key
while (hashArray[hashVal] != null) // until empty cell,
{
if (hashArray[hashVal].getKey() == key)
return hashArray[hashVal]; // found, return item
++hashVal; // go to next cell
hashVal %= arraySize; // wraparound if necessary
}
return null; // can't find item
}
public static void main(String[] args) throws IOException {
DataItem aDataItem;
int aKey, size, initSize, keysPerCell;
size = 150;
initSize = 100;
keysPerCell = 10;
HashTable theHashTable = new HashTable(size);
for (int j = 0; j < initSize; j++){
aKey = (int) (java.lang.Math.random() * keysPerCell * size);
aDataItem = new DataItem(aKey);
theHashTable.insert(aDataItem);
}
theHashTable.displayTable();
aDataItem = new DataItem(100);
theHashTable.insert(aDataItem);
theHashTable.delete(100);
aDataItem = theHashTable.find(100);
if (aDataItem != null) {
System.out.println("Found " + 100);
} else
System.out.println("Could not find " + 100);
}
}
class DataItem {
private int data;
public DataItem(int d) {
data = d;
}
public int getKey() {
return data;
}
}
|
