This assignment is due on 08/02/18 at 11:59:59am.

Task: Implementation of the ProbeHashTable class with linear probing. The template of ProbeHashTable class and relevant classes are given below:

public class ProbeHashTable extends AbstractHashMap { private MapEntry[] table; private MapEntry DEFUNCT = new MapEntry(null,null); //constructors protected void createTable() { // your implementation here } private boolean isAvailable(int i) { // your implementation here } private int findSlot(int h, String k) { // your implementation here } protected Object bucketPut(int h, Object key, Object value) { // your implementation here } protected Object bucketGet(int h, Object key) { // your implementation here } protected Object bucketRemove(int h, Object key) { // your implementation here } public String toString() { // convert the ProbeHashTable object to a string in the format of // "index key value" tuples, for example // 0 CSU OHIO // 1 CLE PIT // 2 PLAY HOUSE } } 

public class MapEntry { private String key; private String value; // constructor public String getKey() {return key;} public String getValue() {return value;} public void setValue(String v) {this.value = v;} public int hashCode() { int h = 0; for (int i=0; i>>27); h += (int)key.charAt(i); } return h; } } 

public abstract class AbstractHashMap extends AbstractMap { protected int n = 0; // the number of entries protected int capacity; // size of the map private int prime; // the prime number private long scale, offset; // a = scale, b = offset public AbstractHashMap() { capacity = 199; prime = 999331; Random rand = new Random(); scale = rand.nextInt(prime-1) + 1; offset = rand.nextInt(prime); createTable(); } public AbstractHashMap(int c, int p, long scale, long off) { this.capacity = c; this.prime = p; this.scale = scale; this.offset = off; createTable(); } public int size() {return n;} public boolean isEmpty() {return n == 0;} public int hashValue(Object key) { return (int) ((Math.abs(key.hashCode()*scale+offset)%prime)%capacity); } public Object get(Object key) { int h = hashValue(key); return bucketGet(h, key); } public Object remove(Object key) { int h = hashValue(key); return bucketRemove(h, key); } public Object put(Object key, Object value) { int h = hashValue(key); return bucketPut(h, key, value); } protected abstract void createTable(); protected abstract Object bucketGet(int h, Object k); protected abstract Object bucketRemove(int h, Object k); protected abstract Object bucketPut(int h, Object k, Object v); } 

public abstract class AbstractMap { public Object get(Object key); public Object remove(Object key); public Object put(Object key, Object value); public int size(); public boolean isEmpty(); } 

Requirements:

Implement the ProbeHashMap class as we discussed in the lectures.

Your implementation has to follow the specification given. Any other implementation (there are tons of HashTable code on the Internet) will not receive any credit.

Test: write a test program to create a hash table with the default size. Insert 100 data items (random strings) and then remove 10 of them. Finally, please print out the remaining items in the hash table. Note that your implementation will be evaluated by a specific test program while being graded.

Bonus: 10 point bonus will be given for those implementation that prints out the number collisions while the 100 data items are inserted into the hash table. Hint: to do that, you may want to change the return type of the put() method to int type, which is the number of collisions. Your README file must state the bonus option you are taking to earn the bonus.

Submission:

Each student submits one copy of the source code: ProbeHashTable.java, AbstractHashMap.java, AbstractMap.java, MapEntry.java and Test.java.

Here is my current code:

import java.util.*; public abstract class AbstractHashMap extends AbstractMap { protected int n = 0; protected int capacity; private int prime; private long scale, offset; public AbstractHashMap() { capacity = 199; prime = 999331; Random rand = new Random(); scale = rand.nextInt(prime-1) + 1; offset = rand.nextInt(prime); createTable(); }

public AbstractHashMap(int c, int p, long scale, long off) { this.capacity = c; this.prime = p; this.scale = scale; this.offset = off; createTable(); }

public int size() {return n;} public boolean isEmpty() {return n == 0;}

public int hashValue(Object key) { return (int) ((Math.abs(key.hashCode()*scale+offset)%prime)%capacity); }

public Object get(Object key) { int h = hashValue(key); return bucketGet(h, key); }

public Object remove(Object key) { int h = hashValue(key); return bucketRemove(h, key); }

public Object put(Object key, Object value) { int h = hashValue(key); return bucketPut(h, key, value); }

protected abstract void createTable(); protected abstract Object bucketGet(int h, Object k); protected abstract Object bucketRemove(int h, Object k); protected abstract Object bucketPut(int h, Object k, Object v); }

public abstract class AbstractMap { public abstract Object get(Object key); public abstract Object remove(Object key); public abstract Object put(Object key, Object value); public abstract int size(); public abstract boolean isEmpty(); }

import java.util.*; public class ProbeHashTable extends AbstractHashMap { private MapEntry[] table; private MapEntry DEFUNCT = new MapEntry(null,null); int currentSize = 0; int maxSize = 100; public ProbeHashTable() { int currentSize = 0; int maxSize = 100; String keys = new String[maxSize]; String vals = new String[maxSize]; }

protected void createTable() { table = (MapEntry[]) new MapEntry[capacity]; // safe cast }

private boolean isAvailable(int i) { return(table[i] == null) || (table[i] == DEFUNCT); }

private int findSlot(int h, String k) { int avail = -1; int i = h; do { if(isAvailable(i)) { if (avail == -1) avail = 1; if (table[i] == null) break; } else if (table[i].getKey().equals(k)) return i; i = (i+1)%capacity; } while(i !=h); return -(avail+1); }

protected Object bucketPut(int h, Object key, Object value) { int i = findSlot(h, (String)key); if(i >= 0) { return table[i].setValue(value); } table[-(i+1)] = new MapEntry(key, value); maxSize++; return table[i].getValue(); }

protected Object bucketGet(int h, Object key) { int i = findSlot(h, (String)key); if(i < 0) return null; return table[i].getValue(); }

protected Object bucketRemove(int h, Object key) { int i = findSlot(h, (String) value); if (i < 0) return null; String answer = (String) table[i].getValue(); table[i] = DEFUNCT; maxSize--; return answer; }

public String toString() { System.out.println(" Hash Table: "); for( int i = 0; i < maxSize; i++) if (keys[i] != null) System.out.println(i + " " + keys[i] +" " + vals[i]); System.out.println(); } }

public class MapEntry { private String key; private String value;

public String getKey() {return key;} public String getValue() {return value;}

public int hashCode() { int h = 0; for (int i=0; i>27;) { h += (int)key.charAt(i); } return h; } }

import java.util.*; public class Test { public static void main(String[] args) { Scanner scan = new Scanner(System.in); System.out.println("Hash Table Test "); ProbeHashTable pht = new ProbeHashTable(); char ch; do { System.out.println(" Hash Table Operations "); System.out.println("1. insert "); System.out.println("2. remove "); System.out.println("3. print hash table "); int choice = scan.nextInt(); switch(choice) { case 1 : System.out.println("Enter index , key and value"); pht.bucketPut(scan.next(), scan.next(), scan.next()); break; case 2 : System.out.println("Enter index , key"); pht.bucketRemove(scan.next(), scan.next() ); break; case 3 : pht.toString(); break; default : System.out.println("Wrong Entry "); break; System.out.println(" Do you want to continue (Type Y or N) "); ch = scan.next().charAt(0); }} while (ch == "Y" || ch == "N"); } }