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作者 Re:请问 Hashtable.containsKey(Object) 是怎样实现的? [Re:dm356]
bluecrystal





发贴: 2788991
积分: 48
于 2005-09-28 00:10 user profilesend a private message to usersearch all posts byselect and copy to clipboard. 
ie only, sorry for netscape users:-)add this post to my favorite list
1 Integer对象的比较用equals或者compareTo;
2 To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the hashCode method and the equals method 这是jdk文档的原话,通常要实现hashCode和equals方法
下面简单给出修改后的代码

import java.util.*;

public class Hashtabletest {

public static void main(String args[])
{
Hashtable hs = new Hashtable();
for(int i = 0; i < 10; i++)
hs.put(new Integer(i), new String(i + "aa"));

if(hs.containsKey(new Integer(0)))
System.out.println("OK");
else
System.out.println("SORRY");

  System.out.println((new Integer(1)).equals(new Integer(1)));

Hashtable hs1 = new Hashtable();
for(int i = 0; i < 10; i++)
hs1.put(new hashelement(i), new String(i + "aa"));

if(hs1.containsKey(new hashelement(0)))
System.out.println("OK");
else
System.out.println("SORRY");
}
}

class hashelement
{
int n = 0;
hashelement(int i)
{
n = i;
}
public int getN() {
   return n;
}
public boolean equals(Object hs) {
   return (this.n == ((hashelement)hs).getN());
}
public int hashCode() {
   return n;
}
}


运行结果为:

OK
true
OK



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话题树型展开
人气 标题 作者 字数 发贴时间
5334 请问 Hashtable.containsKey(Object) 是怎样实现的? dm356 1416 2005-09-27 20:16
6278 Re:请问 Hashtable.containsKey(Object) 是怎样实现的? bluecrystal 1245 2005-09-28 00:10

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