myhash.java

用java编写的hashtable程序

/**
A class for representing the hashtable built with the linked list
Written by : H Yu
*/


public class MyHash {

	//class constants
	public static final int DefaultSIZE = 97;

	//instance variables
	MyLinkedList[] hashtable;
	int tablesize;
	
	//constructors
	
	/**
	*creat an instance of class MyHash with default tablesize
	*/
	public MyHash() {
		tablesize = DefaultSIZE;
		hashtable = new MyLinkedList[tablesize]; 
		for (int i=0;i<tablesize;i++) {
			hashtable[i] = new MyLinkedList() ;
		}
	}

	/**
	*creat an instance of class MyHash with specific parameters
	*@param s size of hashtable
	*/
	public MyHash (int s) {
		tablesize = s;
		hashtable = new MyLinkedList[tablesize];
		for (int i=0;i<tablesize;i++) {
			hashtable[i] = new MyLinkedList();
		}
	}

	//mutator method

	/**
	*insert a word to the hashtable
	*@param w word
	*/
	public void setWord(String w) {
		int index = MyHashFunction.HashFunction(w,tablesize);
		hashtable[index].setWord(w);
	}

	//accessor methods

	/**
	*return true if a word exist in the hashtable
	*@param w word
	*/
	public boolean hasWord(String w) {
		boolean exist=false;
		for(int i=0;i<tablesize;i++) {
			if(hashtable[i].isWord(w)) {
				exist=true;
			}
		}
		return(exist);
	}

	/**
	*return count if w matches to the word in the table
	*return 0 if not
	*@param w word
	*/
	public int getCount(String w) {
		int count = 0;
		for(int i=0;i<tablesize;i++) {
			if(hashtable[i].isWord(w)) {
				count = hashtable[i].getCount(w);
			}
		}
		return(count);
	}

	/**
	*return the index if w matches the word in the list
	*return 100+tablesize if w does not exist in the hashtable
	*@param w word
	*/
	public int getIndex(String w) {
		int index = tablesize+100;
		for(int i=0;i<tablesize;i++) {
			if(hashtable[i].isWord(w)) {
				index = i;
			}
		}
		return(index);
	}

	/**
	*return the length of the list with index i
	*@param i index
	*/
	public int getListLength(int i) {
		int length = 0;
		if(i<tablesize)
			length = hashtable[i].getLength();
		return(length);
	}

	/**
	*return the total number of objects in the hashtable
	*/
	public int getNumber() {
		int number = 0;
		for(int i=0;i<tablesize;i++) {
			if(hashtable[i].getWord(0) != null)
				number += hashtable[i].getLength();
		}
		return(number);
	}

	/**
	*return the word with the index i and j
	*@param i index of hashtable
	*@param j index of list
	*/
	public String getWord(int i,int j) {
		String word = null;
		if(i<tablesize && j <= hashtable[i].getLength()) {
			word=hashtable[i].getWord(j);
		}
		return(word);
	}

	/**
	*return the total number of objects in the hashtable including the dummies
	*/
	public int getTotalNumber() {
		int number = 0;
		for(int i=0;i<tablesize;i++) {
				int l=hashtable[i].getLength();
				number += l+1;
		}
		return(number);
	}

	/**
	*return the hashtable size
	*/
	public int getSize() {
		return(tablesize);
	}

	//print method

	public void PrintHashTable() {		
		for(int i=0;i<tablesize;i++) {			
			System.out.println(hashtable[i]);
		}
	}
}