structure
Class ReverseComparator

java.lang.Object
  |
  +--structure.ReverseComparator
All Implemented Interfaces:
java.util.Comparator

public class ReverseComparator
extends java.lang.Object
implements java.util.Comparator

Implementation of the Comparator interface that provides a compare(Object,Object) method that compares two objects using those objects default compareTo methods. Reverse comparator however, reverses the natural comparison as follows:

Were we to call compare(a,b), ReverseComparator would return the following:

     >0 if a < b
      0 if a = b
     <0 if a > b
 

Example usage:

To print out the equality relationship between two randomly generated integers we could use the following:

 public static void main(String[] argv){
     Random  rand = new Random();
     Comparator c = new ReverseComparator();
      
     //generate two random Integers
     Integer a = new Integer(rand.nextInt(100));
     Integer b = new Integer(rand.nextInt(100));
      
     //print out the proper equality relationship between these integers
     if(c.compare(a,b) > 0) System.out.println("A:" + a + " > B:" + b);
     else if (c.compare(a,b) < 0) System.out.println("A:" + a + " < B:" + b);
     else System.out.println("A:" + a + " = B:" + b);
 

 


Field Summary
protected  java.util.Comparator base
           
 
Constructor Summary
ReverseComparator()
          Construct a comparator that generates reverse natural comparison
ReverseComparator(java.util.Comparator base)
          Construct a comparator that generates reverse of another comparator
 
Method Summary
 int compare(java.lang.Object a, java.lang.Object b)
          Compare two values, a and b.
 boolean equals(java.lang.Object b)
          Returns true if the other object is a NaturalComparator.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

base

protected java.util.Comparator base
Constructor Detail

ReverseComparator

public ReverseComparator()
Construct a comparator that generates reverse natural comparison


ReverseComparator

public ReverseComparator(java.util.Comparator base)
Construct a comparator that generates reverse of another comparator

Parameters:
base - the ordering to be reversed
Method Detail

compare

public int compare(java.lang.Object a,
                   java.lang.Object b)
Compare two values, a and b. Simply calls the default compareTo method for a on b.

Specified by:
compare in interface java.util.Comparator
Parameters:
a - object performing the compare
b - the object being compared
Returns:
value <, ==, > 0 if a <, ==, > b using a.compareTo

equals

public boolean equals(java.lang.Object b)
Returns true if the other object is a NaturalComparator.

Specified by:
equals in interface java.util.Comparator
Overrides:
equals in class java.lang.Object
Parameters:
b - a possible NaturalComparator
Returns:
true if b is a NaturalComparator