现在是夏天！自己看源码不就行了！ public Hashtable(int initialCapacity, float loadFactor) { if (initialCapacity < 0) throw new IllegalArgumentException("Illegal Capacity: "+ initialCapacity); if (loadFactor <= 0 || Float.isNaN(loadFactor)) throw new IllegalArgumentException("Illegal Load: "+loadFactor); if (initialCapacity==0) initialCapacity = 1; this.loadFactor = loadFactor; table = new Entry[initialCapacity]; threshold = (int)(initialCapacity * loadFactor); }
/*---------------------估计LZ也没心情看 * 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; }
/**接上 * 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; } } }
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Capacity: "+
initialCapacity);
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new IllegalArgumentException("Illegal Load: "+loadFactor); if (initialCapacity==0)
initialCapacity = 1;
this.loadFactor = loadFactor;
table = new Entry[initialCapacity];
threshold = (int)(initialCapacity * loadFactor);
}
/*---------------------估计LZ也没心情看
* 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;
}
/**接上
* 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;
}
}
}