com.lowagie.text.pdf.IntHashtable Maven / Gradle / Ivy
// IntHashtable - a Hashtable that uses ints as the keys
//
// This is 90% based on JavaSoft's java.util.Hashtable.
//
// Visit the ACME Labs Java page for up-to-date versions of this and other
// fine Java utilities: http://www.acme.com/java/
package com.lowagie.text.pdf;
import java.util.Arrays;
/// A Hashtable that uses ints as the keys.
//
// Use just like java.util.Hashtable, except that the keys must be ints.
// This is much faster than creating a new Integer for each access.
//
// Fetch the software.
// Fetch the entire Acme package.
//
// @see java.util.Hashtable
public class IntHashtable {
/// The hash table data.
private IntHashtableEntry table[];
/// The total number of entries in the hash table.
private int count;
/// Rehashes the table when count exceeds this threshold.
private int threshold;
/// The load factor for the hashtable.
private float loadFactor;
/// Constructs a new, empty hashtable with the specified initial
// capacity and the specified load factor.
// @param initialCapacity the initial number of buckets
// @param loadFactor a number between 0.0 and 1.0, it defines
// the threshold for rehashing the hashtable into
// a bigger one.
// @exception IllegalArgumentException If the initial capacity
// is less than or equal to zero.
// @exception IllegalArgumentException If the load factor is
// less than or equal to zero.
public IntHashtable( int initialCapacity, float loadFactor ) {
if ( initialCapacity <= 0 || loadFactor <= 0.0 )
throw new IllegalArgumentException();
this.loadFactor = loadFactor;
table = new IntHashtableEntry[initialCapacity];
threshold = (int) ( initialCapacity * loadFactor );
}
/// Constructs a new, empty hashtable with the specified initial
// capacity.
// @param initialCapacity the initial number of buckets
public IntHashtable( int initialCapacity ) {
this( initialCapacity, 0.75f );
}
/// Constructs a new, empty hashtable. A default capacity and load factor
// is used. Note that the hashtable will automatically grow when it gets
// full.
public IntHashtable() {
this( 101, 0.75f );
}
/// Returns the number of elements contained in the hashtable.
public int size() {
return count;
}
/// Returns true if the hashtable contains no elements.
public boolean isEmpty() {
return count == 0;
}
/// Returns true if the specified object is an element of the hashtable.
// This operation is more expensive than the containsKey() method.
// @param value the value that we are looking for
// @exception NullPointerException If the value being searched
// for is equal to null.
// @see IntHashtable#containsKey
public boolean contains( int value ) {
IntHashtableEntry tab[] = table;
for ( int i = tab.length ; i-- > 0 ; ) {
for ( IntHashtableEntry e = tab[i] ; e != null ; e = e.next ) {
if ( e.value == value )
return true;
}
}
return false;
}
/// Returns true if the collection contains an element for the key.
// @param key the key that we are looking for
// @see IntHashtable#contains
public boolean containsKey( int key ) {
IntHashtableEntry tab[] = table;
int hash = key;
int index = ( hash & 0x7FFFFFFF ) % tab.length;
for ( IntHashtableEntry e = tab[index] ; e != null ; e = e.next ) {
if ( e.hash == hash && e.key == key )
return true;
}
return false;
}
/// Gets the object associated with the specified key in the
// hashtable.
// @param key the specified key
// @returns the element for the key or null if the key
// is not defined in the hash table.
// @see IntHashtable#put
public int get( int key ) {
IntHashtableEntry tab[] = table;
int hash = key;
int index = ( hash & 0x7FFFFFFF ) % tab.length;
for ( IntHashtableEntry e = tab[index] ; e != null ; e = e.next ) {
if ( e.hash == hash && e.key == key )
return e.value;
}
return 0;
}
/// Rehashes the content of the table into a bigger table.
// This method is called automatically when the hashtable's
// size exceeds the threshold.
protected void rehash() {
int oldCapacity = table.length;
IntHashtableEntry oldTable[] = table;
int newCapacity = oldCapacity * 2 + 1;
IntHashtableEntry newTable[] = new IntHashtableEntry[newCapacity];
threshold = (int) ( newCapacity * loadFactor );
table = newTable;
for ( int i = oldCapacity ; i-- > 0 ; ) {
for ( IntHashtableEntry old = oldTable[i] ; old != null ; ) {
IntHashtableEntry e = old;
old = old.next;
int index = ( e.hash & 0x7FFFFFFF ) % newCapacity;
e.next = newTable[index];
newTable[index] = e;
}
}
}
/// Puts the specified element into the hashtable, using the specified
// key. The element may be retrieved by doing a get() with the same key.
// The key and the element cannot be null.
// @param key the specified key in the hashtable
// @param value the specified element
// @exception NullPointerException If the value of the element
// is equal to null.
// @see IntHashtable#get
// @return the old value of the key, or null if it did not have one.
public int put( int key, int value ) {
// Makes sure the key is not already in the hashtable.
IntHashtableEntry tab[] = table;
int hash = key;
int index = ( hash & 0x7FFFFFFF ) % tab.length;
for ( IntHashtableEntry e = tab[index] ; e != null ; e = e.next ) {
if ( e.hash == hash && e.key == key ) {
int old = e.value;
e.value = value;
return old;
}
}
if ( count >= threshold ) {
// Rehash the table if the threshold is exceeded.
rehash();
return put( key, value );
}
// Creates the new entry.
IntHashtableEntry e = new IntHashtableEntry();
e.hash = hash;
e.key = key;
e.value = value;
e.next = tab[index];
tab[index] = e;
++count;
return 0;
}
/// Removes the element corresponding to the key. Does nothing if the
// key is not present.
// @param key the key that needs to be removed
// @return the value of key, or null if the key was not found.
public int remove( int key ) {
IntHashtableEntry tab[] = table;
int hash = key;
int index = ( hash & 0x7FFFFFFF ) % tab.length;
for ( IntHashtableEntry e = tab[index], prev = null ; e != null ; prev = e, e = e.next ) {
if ( e.hash == hash && e.key == key ) {
if ( prev != null )
prev.next = e.next;
else
tab[index] = e.next;
--count;
return e.value;
}
}
return 0;
}
/// Clears the hash table so that it has no more elements in it.
public void clear() {
IntHashtableEntry tab[] = table;
for ( int index = tab.length; --index >= 0; )
tab[index] = null;
count = 0;
}
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;
IntHashtableEntry entry = null;
while (true) {
if (entry == null)
while ((index-- > 0) && ((entry = table[index]) == null));
if (entry == null)
break;
IntHashtableEntry e = entry;
entry = e.next;
res[ptr++] = e.key;
}
return res;
}
public int getOneKey() {
if (count == 0)
return 0;
int index = table.length;
IntHashtableEntry entry = null;
while ((index-- > 0) && ((entry = table[index]) == null));
if (entry == null)
return 0;
return entry.key;
}
static class IntHashtableEntry {
int hash;
int key;
int value;
IntHashtableEntry next;
}
}