HashSet

java.lang.Object
- ptolemy.backtrack.util.java.util.AbstractCollection
- - ptolemy.backtrack.util.java.util.AbstractSet
  - - ptolemy.backtrack.util.java.util.HashSet

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, Rollbackable, Collection, Set

Direct Known Subclasses:

LinkedHashSet
```
public class HashSet
extends AbstractSet
implements Set, java.lang.Cloneable, java.io.Serializable, Rollbackable
```
This class provides a HashMap-backed implementation of the Set interface.
Most operations are O(1), assuming no hash collisions. In the worst case (where all hashes collide), operations are O(n). Setting the initial capacity too low will force many resizing operations, but setting the initial capacity too high (or loadfactor too low) leads to wasted memory and slower iteration.
HashSet accepts the null key and null values. It is not synchronized, so if you need multi-threaded access, consider using:
Set s = Collections.synchronizedSet(new HashSet(...));
The iterators are fail-fast, meaning that any structural modification, except for remove() called on the iterator itself, cause the iterator to throw a{

Since:

1.2

Author:

Jon Zeppieri, Eric Blake (ebb9@email.byu.edu)

See Also:

Collection, Set, TreeSet, Collections.synchronizedSet(Set), HashMap, LinkedHashSet, Serialized Form

Status

updated to 1.4

Field Summary
- Fields inherited from class ptolemy.backtrack.util.java.util.AbstractCollection
  $CHECKPOINT, $RECORD$$CHECKPOINT

Constructor Summary

Constructors
Constructor and Description
`HashSet()` Construct a new, empty HashSet whose backing HashMap has the default capacity (11) and loadFacor (0.75).
`HashSet(Collection c)` Construct a new HashSet with the same elements as are in the supplied collection (eliminating any duplicates, of course).
`HashSet(int initialCapacity)` Construct a new, empty HashSet whose backing HashMap has the supplied capacity and the default load factor (0.75).
`HashSet(int initialCapacity, float loadFactor)` Construct a new, empty HashSet whose backing HashMap has the supplied capacity and load factor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`$COMMIT(long timestamp)` Commit changes up to the given timestamp, but not including changes made at timestamp and afterward.
`void`	`$RESTORE(long timestamp, boolean trim)` Restore a previous state to all the private fields of this rollbackable object.
`boolean`	`add(java.lang.Object o)` Adds the given Object to the set if it is not already in the Set.
`void`	`clear()` Empties this Set of all elements; this takes constant time.
`java.lang.Object`	`clone()` Returns a shallow copy of this Set.
`boolean`	`contains(java.lang.Object o)` Returns true if the supplied element is in this Set.
`boolean`	`isEmpty()` Returns true if this set has no elements in it.
`java.util.Iterator`	`iterator()` Returns an Iterator over the elements of this Set, which visits the elements in no particular order.
`boolean`	`remove(java.lang.Object o)` Removes the supplied Object from this Set if it is in the Set.
`int`	`size()` Returns the number of elements in this Set (its cardinality).

Methods inherited from class ptolemy.backtrack.util.java.util.AbstractSet
equals, hashCode, removeAll

Methods inherited from class ptolemy.backtrack.util.java.util.AbstractCollection
$GET$CHECKPOINT, $SET$CHECKPOINT, addAll, containsAll, retainAll, toArray, toArray, toString

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface ptolemy.backtrack.util.java.util.Set
$GET$CHECKPOINT, $SET$CHECKPOINT, addAll, containsAll, equals, hashCode, removeAll, retainAll, toArray, toArray

- Constructor Detail
  - HashSet
```
public HashSet()
```
    Construct a new, empty HashSet whose backing HashMap has the default capacity (11) and loadFacor (0.75).
  - HashSet
```
public HashSet(int initialCapacity)
```
    Construct a new, empty HashSet whose backing HashMap has the supplied capacity and the default load factor (0.75).
    
    Parameters:
    
    initialCapacity - the initial capacity of the backing HashMap
    
    Throws:
    
    java.lang.IllegalArgumentException - if the capacity is negative
  - HashSet
```
public HashSet(int initialCapacity,
               float loadFactor)
```
    Construct a new, empty HashSet whose backing HashMap has the supplied capacity and load factor.
    
    Parameters:
    
    initialCapacity - the initial capacity of the backing HashMap
    
    loadFactor - the load factor of the backing HashMap
    
    Throws:
    
    java.lang.IllegalArgumentException - if either argument is negative, or if loadFactor is POSITIVE_INFINITY or NaN
  - HashSet
```
public HashSet(Collection c)
```
    Construct a new HashSet with the same elements as are in the supplied collection (eliminating any duplicates, of course). The backing storage has twice the size of the collection, or the default size of 11, whichever is greater; and the default load factor (0.75).
    
    Parameters:
    
    c - a collection of initial set elements
    
    Throws:
    
    java.lang.NullPointerException - if c is null
- Method Detail
  - add
```
public boolean add(java.lang.Object o)
```
    Adds the given Object to the set if it is not already in the Set. This set permits a null element.
    
    Specified by:
    
    add in interface Collection
    
    Specified by:
    
    add in interface Set
    
    Overrides:
    
    add in class AbstractCollection
    
    Parameters:
    
    o - the Object to add to this Set
    
    Returns:
    
    true if the set did not already contain o
  - clear
```
public void clear()
```
    Empties this Set of all elements; this takes constant time.
    
    Specified by:
    
    clear in interface Collection
    
    Specified by:
    
    clear in interface Set
    
    Overrides:
    
    clear in class AbstractCollection
    
    See Also:
    
    Iterator.remove()
  - clone
```
public java.lang.Object clone()
```
    Returns a shallow copy of this Set. The Set itself is cloned; its elements are not.
    
    Overrides:
    
    clone in class java.lang.Object
    
    Returns:
    
    a shallow clone of the set
  - contains
```
public boolean contains(java.lang.Object o)
```
    Returns true if the supplied element is in this Set.
    
    Specified by:
    
    contains in interface Collection
    
    Specified by:
    
    contains in interface Set
    
    Overrides:
    
    contains in class AbstractCollection
    
    Parameters:
    
    o - the Object to look for
    
    Returns:
    
    true if it is in the set
  - isEmpty
```
public boolean isEmpty()
```
    Returns true if this set has no elements in it.
    
    Specified by:
    
    isEmpty in interface Collection
    
    Specified by:
    
    isEmpty in interface Set
    
    Overrides:
    
    isEmpty in class AbstractCollection
    
    Returns:
    
    size() == 0.
    
    See Also:
    
    AbstractCollection.size()
  - iterator
```
public java.util.Iterator iterator()
```
    Returns an Iterator over the elements of this Set, which visits the elements in no particular order. For this class, the Iterator allows removal of elements. The iterator is fail-fast, and will throw a ConcurrentModificationException if the set is modified externally.
    
    Specified by:
    
    iterator in interface Collection
    
    Specified by:
    
    iterator in interface Set
    
    Specified by:
    
    iterator in class AbstractCollection
    
    Returns:
    
    a set iterator
    
    See Also:
    
    ConcurrentModificationException
  - remove
```
public boolean remove(java.lang.Object o)
```
    Removes the supplied Object from this Set if it is in the Set.
    
    Specified by:
    
    remove in interface Collection
    
    Specified by:
    
    remove in interface Set
    
    Overrides:
    
    remove in class AbstractCollection
    
    Parameters:
    
    o - the object to remove
    
    Returns:
    
    true if an element was removed
    
    See Also:
    
    Iterator.remove()
  - size
```
public int size()
```
    Returns the number of elements in this Set (its cardinality).
    
    Specified by:
    
    size in interface Collection
    
    Specified by:
    
    size in interface Set
    
    Specified by:
    
    size in class AbstractCollection
    
    Returns:
    
    the size of the set
  - $COMMIT
```
public void $COMMIT(long timestamp)
```
    Description copied from interface: Rollbackable
    
    Commit changes up to the given timestamp, but not including changes made at timestamp and afterward.
    
    Specified by:
    
    $COMMIT in interface Rollbackable
    
    Specified by:
    
    $COMMIT in interface Collection
    
    Specified by:
    
    $COMMIT in interface Set
    
    Overrides:
    
    $COMMIT in class AbstractSet
    
    Parameters:
    
    timestamp - The timestamp.
  - $RESTORE
```
public void $RESTORE(long timestamp,
                     boolean trim)
```
    Description copied from interface: Rollbackable
    
    Restore a previous state to all the private fields of this rollbackable object.
    
    Specified by:
    
    $RESTORE in interface Rollbackable
    
    Specified by:
    
    $RESTORE in interface Collection
    
    Specified by:
    
    $RESTORE in interface Set
    
    Overrides:
    
    $RESTORE in class AbstractSet
    
    Parameters:
    
    timestamp - The timestamp taken at the time when the previous state was recorded.
    
    trim - Whether to delete the records used for the rollback.
    
    See Also:
    
    Checkpoint.rollback(long, boolean)

Class HashSet

Field Summary

Fields inherited from class ptolemy.backtrack.util.java.util.AbstractCollection

Constructor Summary

Method Summary

Methods inherited from class ptolemy.backtrack.util.java.util.AbstractSet

Methods inherited from class ptolemy.backtrack.util.java.util.AbstractCollection

Methods inherited from class java.lang.Object

Methods inherited from interface ptolemy.backtrack.util.java.util.Set

Constructor Detail

HashSet

HashSet

HashSet

HashSet

Method Detail

add

clear

clone

contains

isEmpty

iterator

remove

size

$COMMIT

$RESTORE