Class COM.odi.util.OSTreeMap

java.lang.Object
   |
   +----COM.odi.util.OSTreeMap

public class OSTreeMap

extends Object

implements IPersistent, Map

This class is included in PSE Pro, but not in PSE.

Additional information about OSTreeMap is in the user guide.

The keys are Objects and the values are Objects. Any concrete subclass of OSTreeMap must implement the following two methods, to translate object-keys into byte arrays (the internal format the the B-tree stores):

byte[] keyToByteArray(Object key, byte[] keyEncoding);

Object byteArrayToKey(byte[] keyEncoding);

The following exceptions might be thrown by many of the methods in this class:

DatabaseNotOpenException If the database containing the object is not open.

NoTransactionInProgressException If there is no transaction in progress.

ObjectNotFoundException If the object was not found, either because the object itself, its segment, or its database was destroyed; or because the OSTreeMap was created in a transaction that was subsequently aborted.

ObjectException Ifthe object was local and was fetched in a previous transaction.

ObjectStoreException If the session implied by an argument to the call or the object the method is called on is not the same as the session associated with the current thread.

UpdateReadOnlyException If there is a readonly transaction in progress or if the database is open for readonly.

OSTreeMap(Placement, int, boolean, boolean)

Creates an OSTreeMap.

byteArrayToKey(byte[])

Decodes a byte-array encoding of a key into an instance of the key type.

clear()

Removes all mappings from this Map.

contains(Object)

Returns true if this Map maps one or more keys to this value.

containsKey(Object)

Returns true if this Map contains a mapping for the specified key.

containsValue(Object)

Returns true if this Map maps one or more keys to this value.

entries()

Returns a Collection view of the mappings contained in this Map.

equals(Object)

Compares the specified Object with this Map for equality.

get(Object)

Returns the value to which this Map maps the specified key.

hashCode()

UNSUPPORTED IN THIS RELEASE OF PSE.

isEmpty()

Returns true if this Map contains no key-value mappings.

isSizeMaintained()

Determines if this map maintains its size.

keySet()

Returns a Set view of the keys contained in this Map.

keyToByteArray(Object, byte[])

Encodes a key into a byte array.

maintainSize(boolean)

Modifies the map to maintain or not maintain information about its size.

put(Object, Object)

Associates the specified value with the specified key in this Map (optional operation).

putAll(Map)

Copies all of the mappings from the specified Map to this Map.

remove(Object)

Removes the mapping for this key from this Map if present (optional operation).

size()

Returns the number of key-value mappings in this Map.

sizeEstimate()

For maps that do not maintain their size, returns the size computed by the last call to size().

values()

Returns a Collection view of the values contained in this Map.

  protected OSTreeMap(Placement placement,
                      int keySize,
                      boolean fixedSizeKeys,
                      boolean export)

Creates an OSTreeMap. Note that the database containing the placement needs to be open for update and an update transaction needs to be in progress.

Parameters:

placement - The database or segment in which to create the OSTreeMap.

keySize - The size of the key -- must be a number greater than 0. If variable size keys are permitted, this is the size key which can be stored without using overflow storage. Note that three combinations of key size and key variability are handled specially to provide better efficiency: 4 and 8 byte fixed sized keys, and 28 byte variable sized keys.

fixedSizeKeys - True indicates that the keys have a fixed maximum length of keySize (keys smaller than this fixed maximum behave as if they were padded with zeros to keySize); false indicates that the keys are of variable length, in which case the keySize is interpreted as the size that the btree should attempt to store without recourse to overflow key storage.

export - If true, make the map an exported object.

Throws: NoTransactionInProgressException

If no transaction is in progress.

Throws: ObjectStoreException

If the current thread is not associated with a session and there is no global session.

Throws: UpdateReadOnlyException

If there is a read-only transaction in progress or if the database is open read-only.

  public int size()

Returns the number of key-value mappings in this Map.

  public int sizeEstimate()

For maps that do not maintain their size, returns the size computed by the last call to size(). For other maps, does the same thing as size().

Returns:

The estimated size.

See Also:

isSizeMaintained, maintainSize

  public boolean isSizeMaintained()

Determines if this map maintains its size.

Returns:

True if the map maintains its size, otherwise false.

See Also:

sizeEstimate, maintainSize

  public void maintainSize(boolean maintainSize)

Modifies the map to maintain or not maintain information about its size. Maps maintain their size by default. For maps that maintain their size, putting or removing entries from the map requires a write lock on the top of the tree, which produces a concurrency hot-spot when using ObjectStore. Maps that do not maintain their size do not have this concurrency problem for putting or removing entries, but need to scan the entire tree to determine the size.

Note that iterators on maps which do not maintain their size do not detect concurrent modifications.

Parameters:

maintainSize - If true, causes the map to maintain its size. If false, causes the map to not maintain its size.

See Also:

sizeEstimate, isSizeMaintained

  public boolean isEmpty()

Returns true if this Map contains no key-value mappings.

  public boolean containsValue(Object value)

Returns true if this Map maps one or more keys to this value. More formally, returns true if and only if this Map contains at least one mapping to a value v such that (value==null ? v==null : value.equals(v)).

Parameters:

value - value whose presence in this Map is to be tested.

  public boolean contains(Object value)

Returns true if this Map maps one or more keys to this value. Same as containsValue.

  public boolean containsKey(Object key)

Returns true if this Map contains a mapping for the specified key.

Parameters:

key - key whose presence in this Map is to be tested.

  public Object get(Object key)

Returns the value to which this Map maps the specified key. Returns null if the Map contains no mapping for this key. A return value of null does not necessarily indicate that the Map contains no mapping for the key; it's also possible that the Map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

Parameters:

key - key whose associated value is to be returned.

See Also:

containsKey

  public Object put(Object key,
                    Object value)

Associates the specified value with the specified key in this Map (optional operation). If the Map previously contained a mapping for this key, the old value is replaced.

Parameters:

key - key with which the specified value is to be associated.

value - value to be associated with the specified key.

Returns:

previous value associated with specified key, or null if there was no mapping for key. (A null return can also indicate that the Map previously associated null with the specified key, if the implementation supports null values.)

Throws: ClassCastException

class of the specified key or value prevents it from being stored in this Map.

Throws: IllegalArgumentException

some aspect of this key or value prevents it from being stored in this Map.

Throws: NullPointerException

this Map does not permit null keys or values, and the specified key or value is null.

  public Object remove(Object key)

Removes the mapping for this key from this Map if present (optional operation).

Parameters:

key - key whose mapping is to be removed from the Map.

Returns:

previous value associated with specified key, or null if there was no mapping for key. (A null return can also indicate that the Map previously associated null with the specified key, if the implementation supports null values.)

  public void putAll(Map m)

Copies all of the mappings from the specified Map to this Map. These mappings will replace any mappings that this Map had for any of the keys currently in the specified Map.

Parameters:

t - Mappings to be stored in this Map.

Throws: ClassCastException

class of a key or value in the specified Map prevents it from being stored in this Map.

Throws: IllegalArgumentException

some aspect of a key or value in the specified Map prevents it from being stored in this Map.

Throws: NullPointerException

this Map does not permit null keys or values, and the specified key or value is null.

  public void clear()

Removes all mappings from this Map.

  public Set keySet()

Returns a Set view of the keys contained in this Map. The Set is backed by the Map, so changes to the Map are reflected in the Set, and vice-versa. (If the Map is modified while while an iteration over the Set is in progress, the results of the iteration are undefined.) The Set supports element removal (which removes the corresponding mapping from the Map) via the Iterator.remove, Set.remove, removeAll retainAll, and clear operations. It does not support the add or addAll operations.

  public Collection values()

Returns a Collection view of the values contained in this Map. The Collection is backed by the Map, so changes to the Map are reflected in the Collection, and vice-versa. (If the Map is modified while while an iteration over the Collection is in progress, the results of the iteration are undefined.) The Collection supports element removal (which removes the corresponding mapping from the Map) via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

  public Set entries()

Returns a Collection view of the mappings contained in this Map. Each element in this collection is a Map.Entry. The Collection is backed by the Map, so changes to the Map are reflected in the Collection, and vice-versa. (If the Map is modified while while an iteration over the Collection is in progress, the results of the iteration are undefined.) The Collection supports element removal (which removes the corresponding mapping from the Map) via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

  public boolean equals(Object obj)

Compares the specified Object with this Map for equality. Returns true if the given object is also a Map and the two Maps represent the same mappings. More formally, two Maps t1 and t2 represent the same mappings if t1.keySet().equals(t2.keySet()) and for every key k in t1.keySet(), (t1.get(k)==null ? t2.get(k)==null : t1.get(k).equals(t2.get(k))) . This ensures that the equals method works properly across different implementations of the Map interface.

Parameters:

o - Object to be compared for equality with this Map.

Returns:

true if the specified Object is equal to this Map.

Overrides:

equals in class Object

  public int hashCode()

UNSUPPORTED IN THIS RELEASE OF PSE. THIS METHOD WILL BE CHANGED TO PROVIDE A BEHAVIOR COMPATIBLE WITH THE JDK1.2 MAP SPECIFICATION, WHEN THE JDK1.2 IS RELEASED.

Throws: UnsupportedOperationException

this operation is not supported. Returns the hash code value for this Map. The hash code of a Map is defined to be the sum of the hashCodes of each Entry in the Map's entries view. This ensures that t1.equals(t2) implies that t1.hashCode()==t2.hashCode() for any two Maps t1 and t2, as required by the general contract of Object.hashCode.

Overrides:

hashCode in class Object

See Also:

hashCode, equals, equals

  public abstract byte[] keyToByteArray(Object key,
                                        byte keyEncoding[])

Encodes a key into a byte array. Concrete subclasses of OSTreeMap must implement this method.

Parameters:

key - key to be encoded.

keyEncoding - a byte[] to use as a buffer for the returned encoding. If this is null, or is too small to hold the encoding, then a new byte[] will be alloacated and returned.

  public abstract Object byteArrayToKey(byte key[])

Decodes a byte-array encoding of a key into an instance of the key type. Concrete subclasses of OSTreeMap must implement this method.

Parameters:

key - The byte-array encoding of a key.

Returns:

The key object corresponding to the byte-array encoding.