Hashtable的使用方法介绍

1*****************************************************************
import java.util.Dictionary;
import java.util.Enumeration;
import java.util.Vector;

@SuppressWarnings("rawtypes")
public class HashTable1 extends Dictionary{  //Dictionary是个什么东东？

	private Vector keys = new Vector();
	private Vector values = new Vector();
	
	@Override
	public Enumeration elements() {
		return values.elements();
	}

	@Override
	public Object get(Object key) {
		 int index = keys.indexOf(key);
		 if(index == -1){
			 return null;
		 }
		return values.elementAt(index);
	}

	@Override
	public boolean isEmpty() {
		return keys.isEmpty();
	}

	@Override
	public Enumeration keys() {
		return keys.elements();
	}

	@SuppressWarnings("unchecked")
	@Override
	public Object put(Object key, Object value) {
		 keys.addElement(key);
		 values.addElement(value);
		 return key;
	}

	@Override
	public Object remove(Object key) {
		 int index = keys.indexOf(key);
		 if(index == -1){
			 return null;
		 }
		 keys.removeElementAt(index);
		 Object returnval = values.elementAt(index);
		 values.removeElementAt(index);
		return returnval;
	}

	@Override
	public int size() {
		return keys.size();
	}

	public static void main(String are[]){
		HashTable1 ht = new HashTable1();
		for(char c = 'a' ;c <= 'z';c++){
			ht.put(String.valueOf(c), String.valueOf(c).toUpperCase());
		}
		char [] ca = {'a','e','i','o','u'};
		for(int i=0;i<ca.length;i++){
			System.out.println("Uppercase: "+ht.get(String.valueOf(ca[i])));
		}
	}
}
//Vector 具有的方法：size() removeElementAt() addElement() elements() get() 
// indexOf() elementAt()   等等


2***********************************************************************
import java.util.Hashtable;

class Counter{
	int i=1;
	public String toString(){
		return Integer.toString(i);
	}
}
public class HashTable2 {
	@SuppressWarnings({ "rawtypes", "unchecked" })
	public static void main(String args[]){
		Hashtable ht = new Hashtable();
		for(int i=0;i<1000;i++){
			Integer r = new Integer((int)(Math.random()*20));
			if(ht.containsKey(r)){
				((Counter)ht.get(r)).i++;
			}else{
				ht.put(r, new Counter());
			}
		}
		System.out.println(ht);
	}
}

*******************************************************************
import java.util.*;

public class HashtableTest_1 {
	
	public static void main(String[] args) {
		
		Hashtable<String, String> hh = new Hashtable<String, String>();
		hh.put("a", "name"); // 姓名
		hh.put("b", "age"); // 年龄
		hh.put("c", "address"); // 地址
		hh.put("d", "wage"); // 工资
		
		Enumeration<String> er = hh.keys();//返回此哈希表中的键的枚举
		while (er.hasMoreElements()) {//判断此枚举是否包含更多的元素。
			Object o = er.nextElement();//返回此枚举的下一个元素，也就是key值 
			Object v = hh.get(o); //根据key将	value取出
			System.out.println(o + "=" + v);
		}
		
	}
}