HashTable实现一

几点说明：

1、散列表的每个位置称为桶，一个桶可以有多个槽

2、处理溢出采用：线性探查法

3、这里每个桶只有一个槽，如果要多个可以使用类型HashEntry的二维数组tabl[b][s]

 

看代码：

/** hash tables using linear open addressing and division */package dataStructures;/* 线性探测 */public class HashTable {// top-level nested classprotected static class HashEntry {// data membersprotected Object key;protected Object element;// constructorsprivate HashEntry() {}private HashEntry(Object theKey, Object theElement) {key = theKey;element = theElement;}}// data members of HashTableprotected int divisor; // hash function divisorprotected HashEntry[] table; // hash table arrayprotected int size; // number of elements in table// constructorpublic HashTable(int theDivisor) {divisor = theDivisor;// allocate hash table arraytable = new HashEntry[divisor];}// methods/** @return true iff the table is empty */public boolean isEmpty() {return size == 0;}/** @return current number of elements in the table */public int size() {return size;}/** * search an open addressed hash table for an element with key theKey * * @return location of matching element if found, otherwise return location * where an element with key theKey may be inserted provided the * hash table is not full */private int search(Object theKey) {int i = Math.abs(theKey.hashCode()) % divisor; // home bucketint j = i; // start at home bucketdo {if (table[j] == null || table[j].key.equals(theKey))return j;j = (j + 1) % divisor; // next bucket} while (j != i); // returned to home bucket?return j; // table full}/** * @return element with specified key * @return null if no matching element */public Object get(Object theKey) {// search the tableint b = search(theKey);// see if a match was found at table[b]if (table[b] == null || !table[b].key.equals(theKey))return null; // no matchreturn table[b].element; // matching element}/** * insert an element with the specified key overwrite old element if there * is already an element with the given key * * @throws IllegalArgumentException * when the table is full * @return old element (if any) with key theKey */public Object put(Object theKey, Object theElement) {// search the table for a matching elementint b = search(theKey);// check if matching element foundif (table[b] == null) {// no matching element and table not fulltable[b] = new HashEntry(theKey, theElement);size++;return null;} else {// check if duplicate or table fullif (table[b].key.equals(theKey)) {// duplicate, change// table[b].elementObject elementToReturn = table[b].element;table[b].element = theElement;return elementToReturn;} else// table is fullthrow new IllegalArgumentException("table is full");}}/** output the hash table */public void output() {for (int i = 0; i < divisor; i++)if (table[i] == null)System.out.println("null");elseSystem.out.println(table[i].element);}/** test method */public static void main(String[] args) {HashTable h = new HashTable(11);h.put(new Integer(80), new Integer(80));h.put(new Integer(40), new Integer(40));h.put(new Integer(65), new Integer(65));h.output();System.out.println();h.put(new Integer(58), new Integer(58));h.put(new Integer(24), new Integer(24));h.output();System.out.println();h.put(new Integer(2), new Integer(2));h.put(new Integer(13), new Integer(13));h.put(new Integer(46), new Integer(46));h.put(new Integer(16), new Integer(16));h.put(new Integer(7), new Integer(7));h.put(new Integer(21), new Integer(21));h.output();System.out.println();try {h.put(new Integer(99), new Integer(99));} catch (Exception e) {System.out.println(" No memory for 99");}System.out.println();// update elementh.put(new Integer(7), new Integer(29));h.output();}}