---

问题补充：/*
* Copyright 2001-2004 The Apache Software Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* $Id: Hashtable.java,v 1.4 2004/02/16 22:55:54 minchau Exp $
*/

package com.sun.org.apache.xalan.internal.xsltc.runtime;

import java.util.Enumeration;

/**
* IMPORTANT NOTE:
* This code was taken from Sun's Java1.1 JDK java.util.HashTable.java
* All "synchronized" keywords and some methods we do not need have been
* all been removed.
*/

/**
* Object that wraps entries in the hash-table
* @author Morten Jorgensen
*/
class HashtableEntry {
    int hash;
    Object key;
    Object value;
    HashtableEntry next;

    protected Object clone() {
HashtableEntry entry = new HashtableEntry();
entry.hash = hash;
entry.key = key;
entry.value = value;
entry.next = (next != null) ? (HashtableEntry)next.clone() : null;
return entry;
    }
}

/**
* The main hash-table implementation
*/
public class Hashtable {

    private transient HashtableEntry table[]; // hash-table entries
    private transient int count;              // number of entries
    private int threshold;                    // current size of hash-tabke
    private float loadFactor;                 // load factor

    /**
     * Constructs a new, empty hashtable with the specified initial
     * capacity and the specified load factor.
     */
    public Hashtable(int initialCapacity, float loadFactor) {
if (initialCapacity <= 0) initialCapacity = 11;
if (loadFactor <= 0.0) loadFactor = 0.75f;
this.loadFactor = loadFactor;
table = new HashtableEntry[initialCapacity];
threshold = (int)(initialCapacity * loadFactor);
    }

    /**
     * Constructs a new, empty hashtable with the specified initial capacity
     * and default load factor.
     */
    public Hashtable(int initialCapacity) {
this(initialCapacity, 0.75f);
    }

    /**
     * Constructs a new, empty hashtable with a default capacity and load
     * factor.
     */
    public Hashtable() {
this(101, 0.75f);
    }

    /**
     * Returns the number of keys in this hashtable.
     */
    public int size() {
return count;
    }

    /**
     * Tests if this hashtable maps no keys to values.
     */
    public boolean isEmpty() {
return count == 0;
    }

    /**
     * Returns an enumeration of the keys in this hashtable.
     */
    public Enumeration keys() {
return new HashtableEnumerator(table, true);
    }

    /**
     * Returns an enumeration of the values in this hashtable.
     * Use the Enumeration methods on the returned object to fetch the elements
     * sequentially.
     */
    public Enumeration elements() {
return new HashtableEnumerator(table, false);
    }

    /**
     * Tests if some key maps into the specified value in this hashtable.
     * This operation is more expensive than the <code>containsKey</code>
     * method.
     */
    public boolean contains(Object value) {

if (value == null) throw new NullPointerException();

int i;
HashtableEntry e;
HashtableEntry tab[] = table;

for (i = tab.length ; i-- > 0 ;) {
    for (e = tab[i] ; e != null ; e = e.next) {
if (e.value.equals(value)) {
    return true;
}
    }
}
return false;
    }

    /**
     * Tests if the specified object is a key in this hashtable.
     */
    public boolean containsKey(Object key) {
HashtableEntry e;
HashtableEntry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;

for (e = tab[index] ; e != null ; e = e.next)
    if ((e.hash == hash) && e.key.equals(key))
return true;

return false;
    }

    /**
     * Returns the value to which the specified key is mapped in this hashtable.
     */
    public Object get(Object key) {
HashtableEntry e;
HashtableEntry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;

for (e = tab[index] ; e != null ; e = e.next)
    if ((e.hash == hash) && e.key.equals(key))
return e.value;

return null;
    }

    /**
     * Rehashes the contents of the hashtable into a hashtable with a
     * larger capacity. This method is called automatically when the
     * number of keys in the hashtable exceeds this hashtable's capacity
     * and load factor.
     */
    protected void rehash() {
HashtableEntry e, old;
int i, index;
int oldCapacity = table.length;
HashtableEntry oldTable[] = table;

int newCapacity = oldCapacity * 2 + 1;
HashtableEntry newTable[] = new HashtableEntry[newCapacity];

threshold = (int)(newCapacity * loadFactor);
table = newTable;

for (i = oldCapacity ; i-- > 0 ;) {
    for (old = oldTable[i] ; old != null ; ) {
e = old;
old = old.next;
index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newTable[index];
newTable[index] = e;
    }
}
    }

    /**
     * Maps the specified <code>key</code> to the specified
     * <code>value</code> in this hashtable. Neither the key nor the
     * value can be <code>null</code>.
     * <p>
     * The value can be retrieved by calling the <code>get</code> method
     * with a key that is equal to the original key.
     */
    public Object put(Object key, Object value) {
// Make sure the value is not null
if (value == null) throw new NullPointerException();

// Makes sure the key is not already in the hashtable.
HashtableEntry e;
HashtableEntry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;

for (e = tab[index] ; e != null ; e = e.next) {
    if ((e.hash == hash) && e.key.equals(key)) {
Object old = e.value;
e.value = value;
return old;
    }
}

// Rehash the table if the threshold is exceeded
if (count >= threshold) {
    rehash();
    return put(key, value);
}

// Creates the new entry.
e = new HashtableEntry();
e.hash = hash;
e.key = key;
e.value = value;
e.next = tab[index];
tab[index] = e;
count++;
return null;
    }

    /**
     * Removes the key (and its corresponding value) from this
     * hashtable. This method does nothing if the key is not in the hashtable.
     */
    public Object remove(Object key) {
HashtableEntry e, prev;
HashtableEntry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (e = tab[index], prev = null ; e != null ; prev = e, e = e.next) {
    if ((e.hash == hash) && e.key.equals(key)) {
if (prev != null)
    prev.next = e.next;
else
    tab[index] = e.next;
count--;
return e.value;
    }
}
return null;
    }

    /**
     * Clears this hashtable so that it contains no keys.
     */
    public void clear() {
HashtableEntry tab[] = table;
for (int index = tab.length; --index >= 0; )
    tab[index] = null;
count = 0;
    }

    /**
     * Returns a rather long string representation of this hashtable.
     * Handy for debugging - leave it here!!!
     */
    public String toString() {
int i;
int max = size() - 1;
StringBuffer buf = new StringBuffer();
Enumeration k = keys();
Enumeration e = elements();
buf.append("{");

for (i = 0; i <= max; i++) {
    String s1 = k.nextElement().toString();
    String s2 = e.nextElement().toString();
    buf.append(s1 + "=" + s2);
    if (i < max) buf.append(", ");
}
buf.append("}");
return buf.toString();
    }

    /**
     * A hashtable enumerator class.  This class should remain opaque
     * to the client. It will use the Enumeration interface.
     */
    class HashtableEnumerator implements Enumeration {
boolean keys;
int index;
HashtableEntry table[];
HashtableEntry entry;

HashtableEnumerator(HashtableEntry table[], boolean keys) {
    this.table = table;
    this.keys = keys;
    this.index = table.length;
}

public boolean hasMoreElements() {
    if (entry != null) {
return true;
    }
    while (index-- > 0) {
if ((entry = table[index]) != null) {
    return true;
}
    }
    return false;
}

public Object nextElement() {
    if (entry == null) {
while ((index-- > 0) && ((entry = table[index]) == null));
    }
    if (entry != null) {
HashtableEntry e = entry;
entry = e.next;
return keys ? e.key : e.value;
    }
    return null;
}
    }

}