org.odmg

Interface DCollection

All Superinterfaces:

java.util.Collection, java.lang.Iterable

All Known Subinterfaces:

DArray, DBag, DList, DSet

public interface DCollection
extends java.util.Collection

The base interface for all ODMG collections. The ODMG collections are based on JavaSoft’s collection interfaces. All of the operations defined by the JavaSoft Collection interface are supported by an ODMG implementation of DCollection; the exception UnsupportedOperationException is not thrown when a call is made to any of the Collection methods.

DCollection contains methods used to perform queries on the collection. The OQL query predicate is given as a string with the syntax of the where clause of OQL. The predefined OQL variable this is used inside the predicate to denote the current element of the collection.

Version:

ODMG 3.0

Author:

David Jordan (as Java Editor of the Object Data Management Group)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	existsElement(java.lang.String predicate) Determines whether there is an element of the collection that evaluates to true for the predicate.
DCollection	query(java.lang.String predicate) Evaluate the boolean query predicate for each element of the collection and return a new collection that contains each element that evaluated to true.
java.util.Iterator	select(java.lang.String predicate) Access all of the elements of the collection that evaluate to true for the provided query predicate.
java.lang.Object	selectElement(java.lang.String predicate) Selects the single element of the collection for which the provided OQL query predicate is true.

Methods inherited from interface java.util.Collection

add, addAll, clear, contains, containsAll, equals, hashCode, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray

Method Detail

selectElement

java.lang.Object selectElement(java.lang.String predicate)
                               throws QueryInvalidException

Selects the single element of the collection for which the provided OQL query predicate is true.

Parameters:

predicate - An OQL boolean query predicate.

Returns:

The element that evaluates to true for the predicate. If no element evaluates to true, null is returned.

Throws:

QueryInvalidException - The query predicate is invalid.

select

java.util.Iterator select(java.lang.String predicate)
                          throws QueryInvalidException

Access all of the elements of the collection that evaluate to true for the provided query predicate.

Parameters:

predicate - An OQL boolean query predicate.

Returns:

An iterator used to iterate over the elements that evaluated true for the predicate.

Throws:

QueryInvalidException - The query predicate is invalid.

query

DCollection query(java.lang.String predicate)
                  throws QueryInvalidException

Evaluate the boolean query predicate for each element of the collection and return a new collection that contains each element that evaluated to true.

Parameters:

predicate - An OQL boolean query predicate.

Returns:

A new collection containing the elements that evaluated true for the predicate.

Throws:

QueryInvalidException - The query predicate is invalid.

existsElement

boolean existsElement(java.lang.String predicate)
                      throws QueryInvalidException

Determines whether there is an element of the collection that evaluates to true for the predicate.

Parameters:

predicate - An OQL boolean query predicate.

Returns:

True if there is an element of the collection that evaluates to true for the predicate, otherwise false.

Throws:

QueryInvalidException - The query predicate is invalid.