HashTable.java

package pw.davex;

/**
 * @author Dong Fang
 */
public class HashTable <V> {
    private int mTableSize;
    private int mElementNum;
    private int mAttemptTime;
    private HashEntry[] mTable;

    public HashTable(int pTableSize){
        mElementNum = 0;
        mAttemptTime = 0;
        mTableSize = pTableSize;
        mTable = new HashEntry[mTableSize];
    }

    /**
     * @return the Size of HashTable
     */
    public int size(){
        return mTableSize;
    }

    /**
     * @return the Element stored in HashTable
     */
    public int elementNum(){
        return mElementNum;
    }

    /**
     * Hash the Key
     * @param key
     * @return hash
     */
    private int hash(int key)
    {
        return (key & 0x7FFFFFFF) % mTableSize;
    }

    /**
     * store the key and value into the HashTable
     * @param key
     * @param value
     */
    public synchronized void put(int key, V value)
    {
        // Make sure the value is not null
        if (value == null) {
            throw new NullPointerException();
        }

        int hash = hash(key);

        // Makes sure the key is not already in the hashtable.
        while(mTable[hash] != null)
            hash = hash( hash + 1 );

        mTable[hash] = new HashEntry(hash,key,value);
        // System.out.println("[+] " + key + " - " + hash);
        mElementNum++;
    }

    /**
     * get the value stored in the HashTable by key
     * @param key
     * @return the Value
     */
    public synchronized V get(int key) {
        int hash = hash(key);
        while(mTable[hash] != null)
        {
            mAttemptTime++;
            // System.out.println("[-] Hash: " + hash + " Key: " + key + " hashKey: " + mTable[hash].key);
            if(mTable[hash].key == key)
                return (V) mTable[hash].value;
            hash = hash( hash + 1 );
        }
        return null;
    }

    /**
     * @return The average number of probes for all the searches.
     */
    public int getAvgPro(){
        return mAttemptTime / mElementNum;
    }

    /**
     * reset the Probe attempts time of search
     */
    public void resetAttempt(){
        mAttemptTime = 0;
    }

    public class HashEntry<V> {
        int hash;
        int key;
        V value;

        HashEntry(int pHash, int key, V value) {
            this.hash = pHash;
            this.key = key;
            this.value = value;
        }
    }
}