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com.tangosol.util.comparator
Class SafeComparator

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.comparator.SafeComparator

All Implemented Interfaces:

ExternalizableLite, PortableObject, EntryAwareComparator, QueryMapComparator, Serializable, Comparator

Direct Known Subclasses:

EntryComparator, InverseComparator

public class SafeComparator

extends Base

implements Comparator, QueryMapComparator, EntryAwareComparator, Serializable, ExternalizableLite, PortableObject

Null-safe delegating 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 Comparable interface. <p/> Use SafeComparator.INSTANCE to obtain an instance of non-delegating SafeComparator.

Author:

gg 2002.12.10

Field Summary

static SafeComparator	INSTANCE The trivial SafeComparator.
protected Comparator	m_comparator The wrapped Comparator.

Constructor Summary

SafeComparator()
Default constructor (for ExternalizableLite and PortableObject).

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

Method Summary

int	compare(Object o1, Object o2) Compares its two arguments for order.
int	compareEntries(QueryMap.Entry entry1, QueryMap.Entry entry2) Compare two entries using the underlying comparator.
static int	compareSafe(Comparator comparator, Object o1, Object o2) Compares its two arguments for order.
boolean	equals(Object o) Determine if two comparators are equal.
Comparator	getComparator() Obtain the wrapped Comparator.
int	hashCode() Return the hash code for this comparator.
boolean	isKeyComparator() Specifies whether this comparator expects to compare keys or values.
static boolean	isKeyComparator(Comparator comparator) Check whether the specified comparator expects to compare keys or values.
void	readExternal(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.
String	toString() Return a human-readable description for this Comparator.
void	writeExternal(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.

Field Detail

INSTANCE

public static final SafeComparator INSTANCE

The trivial SafeComparator.

m_comparator

protected Comparator m_comparator

The wrapped Comparator. Could be null.

Constructor Detail

SafeComparator

public SafeComparator()

Default constructor (for ExternalizableLite and PortableObject).

SafeComparator

public SafeComparator(Comparator comparator)

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

Parameters:

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

Method Detail

compare

public int compare(Object o1,
                   Object o2)

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.

Specified by:

compare in interface Comparator

Parameters:

o1 - the first object to be compared

o2 - 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

Throws:

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

compareEntries

public int compareEntries(QueryMap.Entry entry1,
                          QueryMap.Entry entry2)

Compare two entries using the underlying comparator. If the wrapped comparator does not implement the QueryMapComparator interface, revert to the entry values comparison.

Specified by:

compareEntries in interface QueryMapComparator

Parameters:

entry1 - the first entry to compare values from; read-only

entry2 - the second entry to compare values from; read-only

Returns:

a negative integer, zero, or a positive integer as the first entry denotes a value that is is less than, equal to, or greater than the value denoted by the second entry

isKeyComparator

public boolean isKeyComparator()

Specifies whether this comparator expects to compare keys or values.

Specified by:

isKeyComparator in interface EntryAwareComparator

Returns:

true if Entry keys are expected; false otherwise

isKeyComparator

public static boolean isKeyComparator(Comparator comparator)

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

Parameters:

comparator - a Comparator to check

Returns:

true if the comparator expects keys; false otherwise

getComparator

public Comparator getComparator()

Obtain the wrapped Comparator.

Returns:

the wrapped Comparator

compareSafe

public static int compareSafe(Comparator comparator,
                              Object o1,
                              Object o2)

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 Comparable interface.

Parameters:

comparator - a comparator to use for the comparison (optional)

o1 - the first object to be compared

o2 - 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

Throws:

ClassCastException - if the arguments are not Comparable

toString

public String toString()

Return a human-readable description for this Comparator.

Returns:

a String description of the Comparator

equals

public boolean equals(Object o)

Determine if two comparators are equal.

Specified by:

equals in interface Comparator

Parameters:

o - the other comparator

Returns:

true if the passed object is equal to this

See Also:

Object.equals(java.lang.Object), Object.hashCode()

hashCode

public int hashCode()

Return the hash code for this comparator.

Returns:

the hash code value for this comparator

readExternal

public void readExternal(DataInput in)
                  throws 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:

IOException - if an I/O exception occurs

NotActiveException - if the object is not in its initial state, and therefore cannot be deserialized into

writeExternal

public void writeExternal(DataOutput out)
                   throws 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:

IOException - if an I/O exception occurs

readExternal

public void readExternal(PofReader in)
                  throws 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:

IOException - if an I/O error occurs

writeExternal

public void writeExternal(PofWriter out)
                   throws 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:

IOException - if an I/O error occurs

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