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

See Also:

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

Constructor Summary

Constructors

Constructor and Description
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

Modifier and Type	Method and Description
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

getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

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