Class HashSetSeparateChaining


java.lang.Object

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  +--java.util.AbstractCollection

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        +--java.util.AbstractSet

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              +--HashSetSeparateChaining


public class HashSetSeparateChaining
extends java.util.AbstractSet
implements java.util.Set, java.lang.Cloneable, java.io.Serializable

This is the Java version of HashSet, but modified so that the number of comparisons corresponds to the number of time objects are compared. The original Java code stored hash values for a initial comparison. This change makes comparing run times by number of comparisons fairer.
THIS CHANGE KEEPS THE OLD FUNCTIONALITY OF HASHSET, BUT AT A LOWER LEVEL OF EFFICIENCY. RECOMMENDED TO USE THIS CODE ONLY FOR BENCHMARKING.

This class implements the Set interface, backed by a hash table (actually a HashMapSeparateChaining instance). It makes no guarantees as to the iteration order of the set; in particular, it does not guarantee that the order will remain constant over time. This class permits the null element.

This class offers constant time performance for the basic operations (add, remove, contains and size), assuming the hash function disperses the elements properly among the buckets. Iterating over this set requires time proportional to the sum of the HashSetSeparateChaining instance's size (the number of elements) plus the "capacity" of the backing HashMapSeparateChaining instance (the number of buckets). Thus, it's very important not to set the intial capacity too high (or the load factor too low) if iteration performance is important.

Note that this implementation is not synchronized. If multiple threads access a set concurrently, and at least one of the threads modifies the set, it must be synchronized externally. This is typically accomplished by synchronizing on some object that naturally encapsulates the set. If no such object exists, the set should be "wrapped" using the Collections.synchronizedSet method. This is best done at creation time, to prevent accidental unsynchronized access to the HashSetSeparateChaining instance:

     Set s = Collections.synchronizedSet(new HashSetSeparateChaining(...));
 

The iterators returned by this class's iterator method are fail-fast: if the set is modified at any time after the iterator is created, in any way except through the iterator's own remove method, the Iterator throws a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Since:
JDK1.2
See Also:
Collection, Set, TreeSet, Collections#synchronizedSet(Set), HashMapSeparateChaining, Serialized Form

Constructor Summary
HashSetSeparateChaining()
          Constructs a new, empty set; the backing HashMapSeparateChaining instance has default capacity and load factor, which is 0.75.
HashSetSeparateChaining(java.util.Collection c)
          Constructs a new set containing the elements in the specified collection.
HashSetSeparateChaining(int initialCapacity)
          Constructs a new, empty set; the backing HashMapSeparateChaining instance has the specified initial capacity and default load factor, which is 0.75.
HashSetSeparateChaining(int initialCapacity, float loadFactor)
          Constructs a new, empty set; the backing HashMapSeparateChaining instance has the specified initial capacity and the specified load factor.
 
Method Summary
 boolean add(java.lang.Object o)
          Adds the specified element to this set if it is not already present.
 void clear()
          Removes all of the elements from this set.
 java.lang.Object clone()
          Returns a shallow copy of this HashSetSeparateChaining instance: the elements themselves are not cloned.
 boolean contains(java.lang.Object o)
          Returns true if this set contains the specified element.
 boolean isEmpty()
          Returns true if this set contains no elements.
 java.util.Iterator iterator()
          Returns an iterator over the elements in this set.
 boolean remove(java.lang.Object o)
          Removes the given element from this set if it is present.
 int size()
          Returns the number of elements in this set (its cardinality).
 
Methods inherited from class java.util.AbstractSet
equals, hashCode
 
Methods inherited from class java.util.AbstractCollection
addAll, containsAll, removeAll, retainAll, toArray, toArray, toString
 
Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

HashSetSeparateChaining


public HashSetSeparateChaining()
Constructs a new, empty set; the backing HashMapSeparateChaining instance has default capacity and load factor, which is 0.75.

HashSetSeparateChaining


public HashSetSeparateChaining(java.util.Collection c)
Constructs a new set containing the elements in the specified collection. The capacity of the backing HashMapSeparateChaining instance is twice the size of the specified collection or eleven (whichever is greater), and the default load factor (which is 0.75) is used.

HashSetSeparateChaining


public HashSetSeparateChaining(int initialCapacity,
                               float loadFactor)
Constructs a new, empty set; the backing HashMapSeparateChaining instance has the specified initial capacity and the specified load factor.
Parameters:
initialCapacity - the initial capacity of the hash map.
loadFactor - the load factor of the hash map.
Throws:
java.lang.IllegalArgumentException - if the initial capacity is less than zero, or if the load factor is nonpositive.

HashSetSeparateChaining


public HashSetSeparateChaining(int initialCapacity)
Constructs a new, empty set; the backing HashMapSeparateChaining instance has the specified initial capacity and default load factor, which is 0.75.
Parameters:
initialCapacity - the initial capacity of the hash table.
Throws:
java.lang.IllegalArgumentException - if the initial capacity is less than zero.
Method Detail

iterator


public java.util.Iterator iterator()
Returns an iterator over the elements in this set. The elements are returned in no particular order.
Specified by:
iterator in interface java.util.Set
Overrides:
iterator in class java.util.AbstractCollection
Returns:
an Iterator over the elements in this set.
See Also:
ConcurrentModificationException

size


public int size()
Returns the number of elements in this set (its cardinality).
Specified by:
size in interface java.util.Set
Overrides:
size in class java.util.AbstractCollection
Returns:
the number of elements in this set (its cardinality).

isEmpty


public boolean isEmpty()
Returns true if this set contains no elements.
Specified by:
isEmpty in interface java.util.Set
Overrides:
isEmpty in class java.util.AbstractCollection
Returns:
true if this set contains no elements.

contains


public boolean contains(java.lang.Object o)
Returns true if this set contains the specified element.
Specified by:
contains in interface java.util.Set
Overrides:
contains in class java.util.AbstractCollection
Returns:
true if this set contains the specified element.

add


public boolean add(java.lang.Object o)
Adds the specified element to this set if it is not already present.
Specified by:
add in interface java.util.Set
Overrides:
add in class java.util.AbstractCollection
Parameters:
o - element to be added to this set.
Returns:
true if the set did not already contain the specified element.

remove


public boolean remove(java.lang.Object o)
Removes the given element from this set if it is present.
Specified by:
remove in interface java.util.Set
Overrides:
remove in class java.util.AbstractCollection
Parameters:
o - object to be removed from this set, if present.
Returns:
true if the set contained the specified element.

clear


public void clear()
Removes all of the elements from this set.
Specified by:
clear in interface java.util.Set
Overrides:
clear in class java.util.AbstractCollection

clone


public java.lang.Object clone()
Returns a shallow copy of this HashSetSeparateChaining instance: the elements themselves are not cloned.
Returns:
a shallow copy of this set.