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Oracle® Coherence Java API Reference
Release 3.7.0.0

E18683-01


com.tangosol.util.filter
Class PresentFilter

java.lang.Object
  extended by com.tangosol.util.Base
      extended by com.tangosol.util.BitHelper
          extended by com.tangosol.util.ExternalizableHelper
              extended by com.tangosol.util.filter.PresentFilter

All Implemented Interfaces:
ExternalizableLite, PortableObject, Filter, EntryFilter, IndexAwareFilter, java.io.Serializable

public class PresentFilter
extends ExternalizableHelper
implements IndexAwareFilter, ExternalizableLite, PortableObject

Filter which returns true for InvocableMap.Entry objects that currently exist in a Map.

This Filter is intended to be used solely in combination with a ConditionalProcessor and is unnecessary for standard QueryMap operations.

Author:
jh 2005.12.16
See Also:
InvocableMap.Entry.isPresent()

Field Summary
static PresentFilter INSTANCE
          An instance of the PresentFilter.

 

Constructor Summary
PresentFilter()
          Construct a PresentFilter.

 

Method Summary
 Filter applyIndex(java.util.Map mapIndexes, java.util.Set setKeys)
          Filter remaining keys using a Map of available indexes.
 int calculateEffectiveness(java.util.Map mapIndexes, java.util.Set setKeys)
          Given a Map of available indexes, determine if this IndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.
 boolean equals(java.lang.Object o)
          Compare the PresentFilter with another object to determine equality.
 boolean evaluate(java.lang.Object o)
          Apply the test to the object.
 boolean evaluateEntry(java.util.Map.Entry entry)
          Apply the test to a Map Entry.
 int hashCode()
          Determine a hash value for the PresentFilter object according to the general Object.hashCode() contract.
 void readExternal(java.io.DataInput in)
          Restore the contents of this object by loading the object's state from the passed DataInput object.
 void readExternal(PofReader in)
          Restore the contents of a user type instance by reading its state using the specified PofReader object.
 java.lang.String toString()
          Return a human-readable description for this Filter.
 void writeExternal(java.io.DataOutput out)
          Save the contents of this object by storing the object's state into the passed DataOutput object.
 void writeExternal(PofWriter out)
          Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

 

Methods inherited from class com.tangosol.util.BitHelper
countBits, countBits, countBits, indexOfLSB, indexOfLSB, indexOfLSB, indexOfMSB, indexOfMSB, indexOfMSB, rotateLeft, rotateLeft, rotateLeft, rotateRight, rotateRight, rotateRight, toBitString, toBitString, toBitString

 

Field Detail

INSTANCE

public static final PresentFilter INSTANCE
An instance of the PresentFilter.

Constructor Detail

PresentFilter

public PresentFilter()
Construct a PresentFilter.

Method Detail

evaluate

public boolean evaluate(java.lang.Object o)
Apply the test to the object.
Specified by:
evaluate in interface Filter
Parameters:
o - the object to test
Returns:
true if the test passes, false otherwise

evaluateEntry

public boolean evaluateEntry(java.util.Map.Entry entry)
Apply the test to a Map Entry.
Specified by:
evaluateEntry in interface EntryFilter
Parameters:
entry - the Map Entry to evaluate; never null
Returns:
true if the test passes, false otherwise

calculateEffectiveness

public int calculateEffectiveness(java.util.Map mapIndexes,
                                  java.util.Set setKeys)
Given a Map of available indexes, determine if this IndexAwareFilter can use any of the indexes to assist in its processing, and if so, determine how effective the use of that index would be.

The returned value is an effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys. An operation that requires no more than a single access to the index content (i.e. Equals, NotEquals) has an effectiveness of one. Evaluation of a single entry is assumed to have an effectiveness that depends on the index implementation and is usually measured as a constant number of the single operations. This number is referred to as evaluation cost.

If the effectiveness of a filter evaluates to a number larger than the keySet.size() * <evaluation cost> then a user could avoid using the index and iterate through the keySet calling evaluate rather then applyIndex.

Specified by:
calculateEffectiveness in interface IndexAwareFilter
Parameters:
mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only
setKeys - the set of keys that will be filtered; read-only
Returns:
an effectiveness estimate of how well this filter can use the specified indexes to filter the specified keys

applyIndex

public Filter applyIndex(java.util.Map mapIndexes,
                         java.util.Set setKeys)
Filter remaining keys using a Map of available indexes.

The filter is responsible for removing all keys from the passed set of keys that the applicable indexes can prove should be filtered. If the filter does not fully evaluate the remaining keys using just the index information, it must return a filter (which may be an EntryFilter) that can complete the task using an iterating implementation. If, on the other hand, the filter does fully evaluate the remaining keys using just the index information, then it should return null to indicate that no further filtering is necessary.

Specified by:
applyIndex in interface IndexAwareFilter
Parameters:
mapIndexes - the available MapIndex objects keyed by the related ValueExtractor; read-only
setKeys - the mutable set of keys that remain to be filtered
Returns:
a Filter object (which may be an EntryFilter) that can be used to process the remaining keys, or null if no additional filter processing is necessary

equals

public boolean equals(java.lang.Object o)
Compare the PresentFilter with another object to determine equality.
Returns:
true iff this PresentFilter and the passed object are equivalent PresentFilters

hashCode

public int hashCode()
Determine a hash value for the PresentFilter object according to the general Object.hashCode() contract.
Returns:
an integer hash value for this PresentFilter object

toString

public java.lang.String toString()
Return a human-readable description for this Filter.
Returns:
a String description of the Filter

readExternal

public void readExternal(java.io.DataInput in)
                  throws java.io.IOException
Restore the contents of this object by loading the object's state from the passed DataInput object.
Specified by:
readExternal in interface ExternalizableLite
Parameters:
in - the DataInput stream to read data from in order to restore the state of this object
Throws:
java.io.IOException - if an I/O exception occurs
java.io.NotActiveException - if the object is not in its initial state, and therefore cannot be deserialized into

writeExternal

public void writeExternal(java.io.DataOutput out)
                   throws java.io.IOException
Save the contents of this object by storing the object's state into the passed DataOutput object.
Specified by:
writeExternal in interface ExternalizableLite
Parameters:
out - the DataOutput stream to write the state of this object to
Throws:
java.io.IOException - if an I/O exception occurs

readExternal

public void readExternal(PofReader in)
                  throws java.io.IOException
Restore the contents of a user type instance by reading its state using the specified PofReader object.
Specified by:
readExternal in interface PortableObject
Parameters:
in - the PofReader from which to read the object's state
Throws:
java.io.IOException - if an I/O error occurs

writeExternal

public void writeExternal(PofWriter out)
                   throws java.io.IOException
Save the contents of a POF user type instance by writing its state using the specified PofWriter object.
Specified by:
writeExternal in interface PortableObject
Parameters:
out - the PofWriter to which to write the object's state
Throws:
java.io.IOException - if an I/O error occurs

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Oracle® Coherence Java API Reference
Release 3.7.0.0

E18683-01


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