散列表

public class HashList {    
    
    private String[] table;

    private int size;

    private int threshold;

    private static final int INITIAL_CAPACITY = 10;

    private static final int SIZE_INCREASE = 10;

    private static final float DEFAULT_LOAD_FACTOR = 0.75f;
    
    
    
    public HashList(){
        threshold = (int)(INITIAL_CAPACITY*DEFAULT_LOAD_FACTOR);
        table = new String[INITIAL_CAPACITY];
    }
    
    
    
    public HashList(String[] table){
        this.table = table;
    }
    
    
    
    
    /**
     * Get the actual size of the list
     * @return
     */
    public int size(){
        return size;
    }
    
    /**
     * for test
     * @return
     */
    public String[] getElements(){
        return table;
    }
    
    public boolean contains(String element) {
        if (element == null) {
            return false;
        }
        if (element.equals(table[getIndex(element)])) {
            return true;
        }
        return false;
    }
    
    public void add(String element){
        int index = getIndex(element);
        if(size>threshold){
            resize();
        }
        table[index] = element;
        size++;
    }
    
    
    
    //private methods
    /**
     * resize the array
     */
    private void resize(){
        String[] newArray = new String[table.length+SIZE_INCREASE];
        for(int i=0;i<table.length;i++){
            newArray[i] = table[i];
        }
        table = newArray;
        threshold = (int)(table.length*DEFAULT_LOAD_FACTOR);
    }
    
    /**
     * get the index of the element
     * @param element
     * @return
     */
    public int getIndex(String element) {
        return (element.hashCode() & 0x7FFFFFFF) % table.length;
    }    
}