com.sas.collection
Class PredicateEnumeration

com.sas.collection.PredicateEnumeration

All Implemented Interfaces:

java.util.Enumeration

Direct Known Subclasses:

StringPredicateEnumeration

public class PredicateEnumeration
implements java.util.Enumeration

PredicateEnumeration filters an Enumeration by only returning items which satisfy a boolean predicate. PredicateEnumeration is a Decorator class. It takes in its constructor a primary Enumeration and a PredicateInterface. The PredicateEnumeration then acts as an Enumeration. It retrieves values from the primary Enumeration, but only returns items such that the specified boolean predicate returns true. Thus, the PredicateEnumeration acts as a way to filter another enumeration with a boolean test.

See Also:

StringPredicateEnumeration

Constructor Summary

PredicateEnumeration(java.util.Enumeration enumer, com.sas.util.PredicateInterface predicate)
Construct a PredicateEnumeration which filters another enumeration by guarding it's values with a predicate.

Method Summary

boolean	hasMoreElements() Returns true if there are more elements which satisfy the predicate.
java.lang.Object	nextElement() Returns the next element from the enumeration which satisfies the predicate.

Constructor Detail

PredicateEnumeration

public PredicateEnumeration(java.util.Enumeration enumer,
                            com.sas.util.PredicateInterface predicate)

Construct a PredicateEnumeration which filters another enumeration by guarding it's values with a predicate. That is, this filter only returns items via enumer.nextElement() if the predicate is true for those items. hasMoreElements() works by performing a look-ahead and running the predicate (one time) on subsequent items until one is found which satisfies the predicate (it will be returned by the next call to nextElement(), or no more items exist.

Parameters:

enumer - the primary enumeration filtered by this PredicateEnumeration

predicate - the predicate used to filter the primary enumertion. Only items which satisfy htis boolean predicate are returned by nextElement()

Method Detail

hasMoreElements

public boolean hasMoreElements()

Returns true if there are more elements which satisfy the predicate.

Specified by:

hasMoreElements in interface java.util.Enumeration

Returns:

true if there are more elements which satisfy the predicate.

nextElement

public java.lang.Object nextElement()

Returns the next element from the enumeration which satisfies the predicate.

Specified by:

nextElement in interface java.util.Enumeration

Returns:

the next element from the enumeration which satisfies the predicate.