优化变成了忧患：String类的split方法引起的内存泄漏

    public String nextToken() {
	/* 
	 * If next position already computed in hasMoreElements() and
	 * delimiters have changed between the computation and this invocation,
	 * then use the computed value.
	 */

	currentPosition = (newPosition >= 0 && !delimsChanged) ?  
	    newPosition : skipDelimiters(currentPosition);

	/* Reset these anyway */
	delimsChanged = false;
	newPosition = -1;

	if (currentPosition >= maxPosition)
	    throw new NoSuchElementException();
	int start = currentPosition;
	currentPosition = scanToken(currentPosition);
	return str.substring(start, currentPosition);
    }

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

 
class Counter {
  private int i = 1;
  int read() { return i; }
  void increment() { i++; }
}
 
public class SortedWordCount {
  private FileInputStream file;
  private StreamTokenizer st;
  private Hashtable counts = new Hashtable();
  SortedWordCount(String filename)
    throws FileNotFoundException {
    try {
      file = new FileInputStream(filename);
      st = new StreamTokenizer(file);
      st.ordinaryChar('.');
      st.ordinaryChar('-');
    } catch(FileNotFoundException e) {
      System.out.println(
        "Could not open " + filename);
      throw e;
    }
  }
  void cleanup() {
    try {
      file.close();
    } catch(IOException e) {
      System.out.println(
        "file.close() unsuccessful");
    }
  }
  void countWords() {
    try {
      while(st.nextToken() !=
        StreamTokenizer.TT_EOF) {
        String s;
        switch(st.ttype) {
          case StreamTokenizer.TT_EOL:
            s = new String("EOL");
            break;
          case StreamTokenizer.TT_NUMBER:
            s = Double.toString(st.nval);
            break;
          case StreamTokenizer.TT_WORD:
            s = st.sval; // Already a String
            break;
          default: // single character in ttype
            s = String.valueOf((char)st.ttype);
        }
        if(counts.containsKey(s))
          ((Counter)counts.get(s)).increment();
        else
          counts.put(s, new Counter());
      }
    } catch(IOException e) {
      System.out.println(
        "st.nextToken() unsuccessful");
    }
  }
  Enumeration values() {
    return counts.elements();
  }
  Enumeration keys() { return counts.keys(); }
  Counter getCounter(String s) {
    return (Counter)counts.get(s);
  }
  Enumeration sortedKeys() {
    Enumeration e = counts.keys();
    StrSortVector sv = new StrSortVector();
    while(e.hasMoreElements())
      sv.addElement((String)e.nextElement());
    // This call forces a sort:
    return sv.elements();
  }
  public static void main(String[] args) {
    try {
      SortedWordCount wc =
        new SortedWordCount(args[0]);
      wc.countWords();
      Enumeration keys = wc.sortedKeys();
      while(keys.hasMoreElements()) {
        String key = (String)keys.nextElement();
        System.out.println(key 
                 + wc.getCounter(key).read());
      }
      wc.cleanup();
    } catch(Exception e) {
      e.printStackTrace();
    }
  }
}