com.itextpdf.io.util.IntHashtable Maven / Gradle / Ivy
/*
This file is part of the iText (R) project.
Copyright (c) 1998-2019 iText Group NV
Authors: Bruno Lowagie, Paulo Soares, et al.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License version 3
as published by the Free Software Foundation with the addition of the
following permission added to Section 15 as permitted in Section 7(a):
FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
OF THIRD PARTY RIGHTS
This program is distributed in the hope that it will be useful, but
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or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program; if not, see http://www.gnu.org/licenses or write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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The interactive user interfaces in modified source and object code versions
of this program must display Appropriate Legal Notices, as required under
Section 5 of the GNU Affero General Public License.
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a covered work must retain the producer line in every PDF that is created
or manipulated using iText.
You can be released from the requirements of the license by purchasing
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develop commercial activities involving the iText software without
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These activities include: offering paid services to customers as an ASP,
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For more information, please contact iText Software Corp. at this
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*/
package com.itextpdf.io.util;
import java.io.Serializable;
import java.util.Arrays;
/**
* A hash map that uses primitive ints for the key rather than objects.
*
* Note that this class is for internal optimization purposes only, and may
* not be supported in future releases of Jakarta Commons Lang. Utilities of
* this sort may be included in future releases of Jakarta Commons Collections.
*
* @author Justin Couch
* @author Alex Chaffee ([email protected])
* @author Stephen Colebourne
* @author Bruno Lowagie (change Objects as keys into int values)
* @author Paulo Soares (added extra methods)
*/
public class IntHashtable implements Cloneable, Serializable {
private static final long serialVersionUID = 7354463962269093965L;
/***
* The hash table data.
*/
private Entry[] table;
/***
* The total number of entries in the hash table.
*/
private int count;
/***
* The table is rehashed when its size exceeds this threshold. (The
* value of this field is (int)(capacity * loadFactor).)
*
* @serial
*/
private int threshold;
/***
* The load factor for the hashtable.
*
* @serial
*/
private float loadFactor;
/***
* Constructs a new, empty hashtable with a default capacity and load
* factor, which is 20 and 0.75 respectively.
*/
public IntHashtable() {
this(150, 0.75f);
}
/***
* Constructs a new, empty hashtable with the specified initial capacity
* and default load factor, which is 0.75.
*
* @param initialCapacity the initial capacity of the hashtable.
* @throws IllegalArgumentException if the initial capacity is less
* than zero.
*/
public IntHashtable(int initialCapacity) {
this(initialCapacity, 0.75f);
}
/***
* Constructs a new, empty hashtable with the specified initial
* capacity and the specified load factor.
*
* @param initialCapacity the initial capacity of the hashtable.
* @param loadFactor the load factor of the hashtable.
* @throws IllegalArgumentException if the initial capacity is less
* than zero, or if the load factor is nonpositive.
*/
public IntHashtable(int initialCapacity, float loadFactor) {
if (initialCapacity < 0) {
throw new IllegalArgumentException(MessageFormatUtil.format("Illegal Capacity: {0}", initialCapacity));
}
if (loadFactor <= 0) {
throw new IllegalArgumentException(MessageFormatUtil.format("Illegal Load: {0}", loadFactor));
}
if (initialCapacity == 0) {
initialCapacity = 1;
}
this.loadFactor = loadFactor;
table = new Entry[initialCapacity];
threshold = (int) (initialCapacity * loadFactor);
}
public IntHashtable(IntHashtable o) {
this(o.table.length, o.loadFactor);
}
/***
* Returns the number of keys in this hashtable.
*
* @return the number of keys in this hashtable.
*/
public int size() {
return count;
}
/***
* Tests if this hashtable maps no keys to values.
*
* @return true if this hashtable maps no keys to values;
* false otherwise.
*/
public boolean isEmpty() {
return count == 0;
}
/***
* Tests if some key maps into the specified value in this hashtable.
* This operation is more expensive than the containsKey
* method.
*
* Note that this method is identical in functionality to containsValue,
* (which is part of the Map interface in the collections framework).
*
* @param value a value to search for.
* @return true if and only if some key maps to the
* value argument in this hashtable as
* determined by the equals method;
* false otherwise.
* @throws NullPointerException if the value is null.
* @see #containsKey(int)
* @see #containsValue(int)
* @see java.util.Map
*/
public boolean contains(int value) {
Entry[] tab = table;
for (int i = tab.length; i-- > 0;) {
for (Entry e = tab[i]; e != null; e = e.next) {
if (e.value == value) {
return true;
}
}
}
return false;
}
/***
* Returns true if this HashMap maps one or more keys
* to this value.
*
* Note that this method is identical in functionality to contains
* (which predates the Map interface).
*
* @param value value whose presence in this HashMap is to be tested.
* @return boolean true if the value is contained
* @see java.util.Map
*/
public boolean containsValue(int value) {
return contains(value);
}
/***
* Tests if the specified int is a key in this hashtable.
*
* @param key possible key.
* @return true if and only if the specified int is a
* key in this hashtable, as determined by the equals
* method; false otherwise.
* @see #contains(int)
*/
public boolean containsKey(int key) {
Entry[] tab = table;
int index = (key & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.key == key) {
return true;
}
}
return false;
}
/***
* Returns the value to which the specified key is mapped in this map.
*
* @param key a key in the hashtable.
* @return the value to which the key is mapped in this hashtable;
* 0 if the key is not mapped to any value in
* this hashtable.
* @see #put(int, int)
*/
public int get(int key) {
Entry[] tab = table;
int index = (key & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.key == key) {
return e.value;
}
}
return 0;
}
/***
* Returns thes value to which the specified key is mapped in this map.
*
* @param key a key in the hashtable.
* @return the values to which the key is mapped in this hashtable;
* null if the key is not mapped to any value in
* this hashtable.
* @see #put(int, int)
public ArrayList getValues(int key) {
Entry[] tab = table;
int index = (key & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.key == key) {
return e.values;
}
}
return null;
}
*/
/***
* Increases the capacity of and internally reorganizes this
* hashtable, in order to accommodate and access its entries more
* efficiently.
*
* This method is called automatically when the number of keys
* in the hashtable exceeds this hashtable's capacity and load
* factor.
*/
protected void rehash() {
int oldCapacity = table.length;
Entry[] oldMap = table;
int newCapacity = oldCapacity * 2 + 1;
Entry[] newMap = new Entry[newCapacity];
threshold = (int) (newCapacity * loadFactor);
table = newMap;
for (int i = oldCapacity; i-- > 0;) {
for (Entry old = oldMap[i]; old != null;) {
Entry e = old;
old = old.next;
int index = (e.key & 0x7FFFFFFF) % newCapacity;
e.next = newMap[index];
newMap[index] = e;
}
}
}
/***
* Maps the specified key to the specified
* value in this hashtable. The key cannot be
* null.
*
* The value can be retrieved by calling the get method
* with a key that is equal to the original key.
*
* @param key the hashtable key.
* @param value the value.
* @return the previous value of the specified key in this hashtable,
* or null if it did not have one.
* @throws NullPointerException if the key is null.
* @see #get(int)
*/
public int put(int key, int value) {
// Makes sure the key is not already in the hashtable.
Entry[] tab = table;
int index = (key & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.key == key) {
int old = e.value;
//e.addValue(old);
e.value = value;
return old;
}
}
if (count >= threshold) {
// Rehash the table if the threshold is exceeded
rehash();
tab = table;
index = (key & 0x7FFFFFFF) % tab.length;
}
// Creates the new entry.
Entry e = new Entry(key, value, tab[index]);
tab[index] = e;
count++;
return 0;
}
/***
* Removes the key (and its corresponding value) from this
* hashtable.
*
* This method does nothing if the key is not present in the
* hashtable.
*
* @param key the key that needs to be removed.
* @return the value to which the key had been mapped in this hashtable,
* or null if the key did not have a mapping.
*/
public int remove(int key) {
Entry[] tab = table;
int index = (key & 0x7FFFFFFF) % tab.length;
Entry e;
Entry prev;
for (e = tab[index], prev = null; e != null; prev = e, e = e.next) {
if (e.key == key) {
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
count--;
int oldValue = e.value;
e.value = 0;
return oldValue;
}
}
return 0;
}
/***
* Clears this hashtable so that it contains no keys.
*/
public void clear() {
Entry[] tab = table;
for (int index = tab.length; --index >= 0;) {
tab[index] = null;
}
count = 0;
}
/***
* Innerclass that acts as a datastructure to create a new entry in the
* table.
*/
public static class Entry implements Serializable {
private static final long serialVersionUID = 8057670534065316193L;
int key;
int value;
//ArrayList values = new ArrayList();
Entry next;
/**
* Create a new entry with the given values.
*
* @param key The key used to enter this in the table
* @param value The value for this key
* @param next A reference to the next entry in the table
*/
Entry(int key, int value, Entry next) {
this.key = key;
this.value = value;
this.next = next;
//values.add(value);
}
// extra methods for inner class Entry by Paulo
public int getKey() {
return key;
}
public int getValue() {
return value;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return new Entry(key, value, next != null ? (Entry)next.clone() : null);
}
@Override
public String toString() {
return MessageFormatUtil.format("{0}={1}", key, value);
}
}
public int[] toOrderedKeys() {
int[] res = getKeys();
Arrays.sort(res);
return res;
}
public int[] getKeys() {
int[] res = new int[count];
int ptr = 0;
int index = table.length;
Entry entry = null;
while (true) {
if (entry == null)
while (index-- > 0 && (entry = table[index]) == null);
if (entry == null)
break;
Entry e = entry;
entry = e.next;
res[ptr++] = e.key;
}
return res;
}
public int getOneKey() {
if (count == 0)
return 0;
int index = table.length;
Entry entry = null;
while (index-- > 0 && (entry = table[index]) == null);
if (entry == null)
return 0;
return entry.key;
}
@Override
public Object clone() throws CloneNotSupportedException {
try {
IntHashtable t = new IntHashtable(this);
t.table = new Entry[table.length];
for (int i = table.length ; i-- > 0 ; ) {
t.table[i] = table[i] != null
? (Entry)table[i].clone() : null;
}
return t;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
}