Package org.apache.commons.collections.comparators

Class BooleanComparator

java.lang.Object
org.apache.commons.collections.comparators.BooleanComparator
All Implemented Interfaces:
Serializable, Comparator
public final class BooleanComparator extends Object implements Comparator, 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 14:33:15 +0200 (Thu, 10 Apr 2008) $
Author:
Rodney Waldhoff
See Also:

  • Constructor Details

    • 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 Details

    • 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(Object obj1, 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 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:
      ClassCastException - when either argument is not Boolean

    • compare

      public int compare(Boolean b1, 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:
      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 Object
      Returns:
      a hash code for this comparator.

    • equals

      public boolean equals(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 Comparator
      Overrides:
      equals in class 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