大侠请进！

[seemee]

各位大侠，请运行下面例子。

关键是如何退出循环？？

/**
@version 1.00 1999-07-07
@author Cay Horstmann
*/

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

/**
This program uses a set to print all unique words in
System.in.
*/
public class SetTest
{
public static void main(String[] args)
{
Set words = new HashSet(59999);
// set to HashSet, LinkedHashSet or TreeSet
long totalTime = 0;

try
{
BufferedReader in = new
BufferedReader(new InputStreamReader(System.in));
String line ;
while ((line = in.readLine()) != null)
{

StringTokenizer tokenizer = new StringTokenizer(line);
System.out.println(tokenizer.toString());
while (tokenizer.hasMoreTokens())
{
String word = tokenizer.nextToken();
long callTime = System.currentTimeMillis();
words.add(word);
callTime = System.currentTimeMillis() - callTime;
totalTime += callTime;
}
}
}
catch (IOException e)
{
System.out.println("Error " + e);
}

Iterator iter = words.iterator();
while (iter.hasNext())
System.out.println(iter.next());
System.out.println(words.size()
+ " distinct words. " + totalTime + " milliseconds.");
}
}

[9731boy]

:)
while ((line = in.readLine()) != null) 吗?
不明白java里的某些怪怪的功能.