Hashtable用法（二）

Hashtable基本用法概述

Hashtable-哈希表类

以哈希表的形式存储数据,数据的形式是键值对.
特点:
查找速度快,遍历相对慢
键值不能有空指针和重复数据

创建
Hashtable ht=new Hashtable();

添值

ht.put(1,"Andy");
ht.put(2,"Bill");
ht.put(3,"Cindy");
ht.put(4,"Dell");
ht.put(5,"Felex");
ht.put(6,"Edinburg");
ht.put(7,"Green");

取值

String str=ht.get(1);
System.out.println(str);// Andy

对键进行遍历

Iterator it = ht.keySet().iterator();

while (it.hasNext()) {
    Integer key = (Integer)it.next();
    System.out.println(key);
}

对值进行遍历

Iterator it = ht.values().iterator();

while (it.hasNext()) {
    String value =(String) it.next();
    System.out.println(value);
}

取Hashtable记录数

Hashtable ht=new Hashtable();

ht.put(1,"Andy");
ht.put(2,"Bill");
ht.put(3,"Cindy");
ht.put(4,"Dell");
ht.put(5,"Felex");
ht.put(6,"Edinburg");
ht.put(7,"Green");

int i=ht.size();// 7

删除元素

Hashtable ht=new Hashtable();

ht.put(1,"Andy");
ht.put(2,"Bill");
ht.put(3,"Cindy");
ht.put(4,"Dell");
ht.put(5,"Felex");
ht.put(6,"Edinburg");
ht.put(7,"Green");

ht.remove(1);
ht.remove(2);
ht.remove(3);
ht.remove(4);

System.out.println(ht.size());// 3

Iterator it = ht.values().iterator();

while (it.hasNext()) {
        // Get value
    String value =(String) it.next();
    System.out.println(value);
}

输出:
3
Green
Edinburg
Felex

 

转载于:https://www.cnblogs.com/zhchongyao/archive/2009/08/12/1544429.html