org.apache.commons.collections.comparators
Class BooleanComparator

java.lang.Object
  org.apache.commons.collections.comparators.BooleanComparator

All Implemented Interfaces:

java.io.Serializable, java.util.Comparator

public final class BooleanComparator
extends java.lang.Object
implements java.util.Comparator, java.io.Serializable

A Comparator for Boolean objects that can sort either true or false first.

Since:

Commons Collections 3.0

Version:

$Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $

Author:

Rodney Waldhoff

See Also:

getTrueFirstComparator(), getFalseFirstComparator(), getBooleanComparator(boolean), Serialized Form

Constructor Summary

BooleanComparator()
Creates a BooleanComparator that sorts false values before true values.

BooleanComparator(boolean trueFirst)
Creates a BooleanComparator that sorts trueFirst values before !trueFirst values.

Method Summary

int	compare(java.lang.Boolean b1, java.lang.Boolean b2) Compares two non-null Boolean objects according to the value of sortsTrueFirst().
int	compare(java.lang.Object obj1, java.lang.Object obj2) Compares two arbitrary Objects.
boolean	equals(java.lang.Object object) Returns true iff that Object is is a Comparator whose ordering is known to be equivalent to mine.
static BooleanComparator	getBooleanComparator(boolean trueFirst) Returns a BooleanComparator instance that sorts trueFirst values before !trueFirst values.
static BooleanComparator	getFalseFirstComparator() Returns a BooleanComparator instance that sorts false values before true values.
static BooleanComparator	getTrueFirstComparator() Returns a BooleanComparator instance that sorts true values before false values.
int	hashCode() Implement a hash code for this comparator that is consistent with equals.
boolean	sortsTrueFirst() Returns true iff I sort true values before false values.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BooleanComparator

public BooleanComparator()

Creates a BooleanComparator that sorts false values before true values.

Equivalent to BooleanComparator(false).

Please use the static factory instead whenever possible.

BooleanComparator

public BooleanComparator(boolean trueFirst)

Creates a BooleanComparator that sorts trueFirst values before !trueFirst values.

Please use the static factories instead whenever possible.

Parameters:

trueFirst - when true, sort true boolean values before false

Method Detail

getTrueFirstComparator

public static BooleanComparator getTrueFirstComparator()

Returns a BooleanComparator instance that sorts true values before false values.

Clients are encouraged to use the value returned from this method instead of constructing a new instance to reduce allocation and garbage collection overhead when multiple BooleanComparators may be used in the same virtual machine.

Returns:

the true first singleton BooleanComparator

getFalseFirstComparator

public static BooleanComparator getFalseFirstComparator()

Returns a BooleanComparator instance that sorts false values before true values.

Clients are encouraged to use the value returned from this method instead of constructing a new instance to reduce allocation and garbage collection overhead when multiple BooleanComparators may be used in the same virtual machine.

Returns:

the false first singleton BooleanComparator

getBooleanComparator

public static BooleanComparator getBooleanComparator(boolean trueFirst)

Returns a BooleanComparator instance that sorts trueFirst values before !trueFirst values.

Clients are encouraged to use the value returned from this method instead of constructing a new instance to reduce allocation and garbage collection overhead when multiple BooleanComparators may be used in the same virtual machine.

Parameters:

trueFirst - when true, sort true Booleans before false

Returns:

a singleton BooleanComparator instance

compare

public int compare(java.lang.Object obj1,
                   java.lang.Object obj2)

Compares two arbitrary Objects. When both arguments are Boolean, this method is equivalent to compare((Boolean)obj1,(Boolean)obj2). When either argument is not a Boolean, this methods throws a ClassCastException.

Specified by:

compare in interface java.util.Comparator

Parameters:

obj1 - the first object to compare

obj2 - the second object to compare

Returns:

negative if obj1 is less, positive if greater, zero if equal

Throws:

java.lang.ClassCastException - when either argument is not Boolean

compare

public int compare(java.lang.Boolean b1,
                   java.lang.Boolean b2)

Compares two non-null Boolean objects according to the value of sortsTrueFirst().

Parameters:

b1 - the first boolean to compare

b2 - the second boolean to compare

Returns:

negative if obj1 is less, positive if greater, zero if equal

Throws:

java.lang.NullPointerException - when either argument null

hashCode

public int hashCode()

Implement a hash code for this comparator that is consistent with equals.

Overrides:

hashCode in class java.lang.Object

Returns:

a hash code for this comparator.

equals

public boolean equals(java.lang.Object object)

Returns true iff that Object is is a Comparator whose ordering is known to be equivalent to mine.

This implementation returns true iff that is a BooleanComparator whose value of sortsTrueFirst() is equal to mine.

Specified by:

equals in interface java.util.Comparator

Overrides:

equals in class java.lang.Object

Parameters:

object - the object to compare to

Returns:

true if equal

sortsTrueFirst

public boolean sortsTrueFirst()

Returns true iff I sort true values before false values. In other words, returns true iff compare(Boolean.FALSE,Boolean.TRUE) returns a positive value.

Returns:

the trueFirst flag