C++ API Reference for Oracle® Coherence Community Edition: SafeComparator Class Reference

Detailed Description

comparator

NULL values are evaluated as "less then" any non-null value. If the wrapped comparator is not specified then all non-null values must implement the coherence::util::Comparable interface. Use SafeComparator::getInstance to obtain an instance of non-delegating SafeComparator.

Author:

djl 2008.05.05

Public Types

typedef spec::Handle

Handle

SafeComparator Handle definition.

typedef spec::View

View

SafeComparator View definition.

typedef spec::Holder

Holder

SafeComparator Holder definition.

Public Member Functions

virtual int32_t

compare (Object::View vO1, Object::View vO2) const

Compares its two arguments for order.

virtual int32_t

compareEntries (QueryMap::Entry::View vEntry1, QueryMap::Entry::View vEntry2) const

Compare two entries using the underlying comparator.

virtual bool

isKeyComparator () const

Specifies whether this comparator expects to compare keys or values.

Returns:: true if Entry keys are expected; false otherwise

virtual void

readExternal (PofReader::Handle hIn)

virtual void

writeExternal (PofWriter::Handle hOut) const

virtual bool

equals (Object::View v) const

virtual size32_t

hashCode () const

Return a hash code value for the Object.

This method is supported for the benefit of hash-based containers.

The general contract of hashCode is:

Whenever it is invoked on the same Object more than once during an execution of an application, the hashCode method must consistently return the same value, provided no information used in equals comparisons on the object is modified. This value need not remain consistent from one execution of an application to another execution of the same application.
If two Objects are equal according to the equals method, then calling the hashCode method on each of the two Objects must produce the same value.
It is not required that if two Objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct results. However, the programmer should be aware that producing distinct results for unequal objects may improve the performance of hash-based containers.

The default implementation is identity based.

Returns:: a hash code value for this Object

virtual TypedHandle
< const String >

toString () const

Output a human-readable description of this Object to the given stream.

Note that when overriding this method the return type must be TypedHandle<const String> rather then String::View. These two types are assignment compatible but not equivalent and declaring the override with String::View will not be a compatible override.

coherence::lang::operator<<(std::ostream, Object::View) is defined and will call into the toString method, to output Objects. If a managed String object is desired, the COH_TO_STRING macro can be used to build up a String from streamable contents and is generally how toString() will be implemented.

 Object::View vKey   = ...
 Object::View vValue = ...
 std::cout << vKey << " = " << vValue << std::endl;

 String::View vs = COH_TO_STRING(vKey << " = " << vValue);

The COH_TO_STRING macro is also the most common way to implement the toString method. For example:

 virtual TypedHandle<const String> Person::toString() const
     {
     return COH_TO_STRING("Name: " << f_sName << " SSN: " << f_nSSN);
     }

Returns:: a string representation of this object

virtual Comparator::View

getComparator () const

Obtain the wrapped Comparator.

Static Public Member Functions

static bool

isKeyComparator (Comparator::View vComparator)

Check whether the specified comparator expects to compare keys or values.

static int32_t

compareSafe (Comparator::View vComparator, Object::View vO1, Object::View vO2)

Compares its two arguments for order.

static
SafeComparator::Handle

getInstance ()

An instance of the SafeComparator.

Protected Member Functions

SafeComparator ()

Default constructor (necessary for the PortableObject interface).

SafeComparator (Comparator::View vComparator)

Construct a SafeComparator delegating to the specified (wrapped) comparator.

Protected Attributes

FinalView< Comparator >

f_vComparator

The wrapped Comparator.

Constructor & Destructor Documentation

SafeComparator ( Comparator::View vComparator ) [protected]

Construct a SafeComparator delegating to the specified (wrapped) comparator.

Parameters:

vComparator

Comparator object to delegate comparison of non-null values (optional)

Member Function Documentation

virtual int32_t compare	(	Object::View	vO1,
		Object::View	vO2
	)			const `[virtual]`

Compares its two arguments for order.

Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second. Null values are evaluated as "less then" any non-null value. If the wrapped comparator is not specified, all non-null values must implement the Comparable interface.

Parameters:

	vO1	the first object to be compared
	vO2	the second object to be compared

Returns:: a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second

Exceptions:

ClassCastException

if the arguments' types prevent them from being compared by this Comparator.

Implements Comparator.

Reimplemented in EntryComparator, and InverseComparator.

virtual int32_t compareEntries	(	QueryMap::Entry::View	vEntry1,
		QueryMap::Entry::View	vEntry2
	)			const `[virtual]`

Compare two entries using the underlying comparator.

If the wrapped comparator does not implement the QueryMapComparator interface, revert to the entry values comparison.

Implements QueryMapComparator.

Reimplemented in InverseComparator.

static bool isKeyComparator ( Comparator::View vComparator ) [static]

Check whether the specified comparator expects to compare keys or values.

Parameters:

vComparator

a Comparator to check

Returns:: true if the comparator expects keys; false otherwise

virtual Comparator::View getComparator ( ) const [virtual]

Obtain the wrapped Comparator.

Returns:: the wrapped Comparator

static int32_t compareSafe	(	Comparator::View	vComparator,
		Object::View	vO1,
		Object::View	vO2
	)			`[static]`

Compares its two arguments for order.

Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second. Null values are evaluated as "less then" any non-null value. Non-null values must implement the coherence::util::Comparable interface.

Parameters:

	vComparator	a comparator to use for the comparison (optional)
	vO1	the first object to be compared
	vO2	the second object to be compared

Returns:: a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second

Exceptions:

ClassCastException

if the arguments are not Comparable

Member Data Documentation

FinalView<Comparator> f_vComparator [protected]

The wrapped Comparator.

Could be null.