root/trunk/Cost.java

// Cost - copyright Tom Felker <tfelker2@uiuc.edu>, December 2004
//
// This represents the badness of getting from one node to another.  It's a
// class because later it may wrap more than an number - we may implement
// uncertainty, probability, walking distance vs. bus distance being different,
// etc...

// NOTE: this can be modified with add(), so you must be careful not to modify
// Costs that are members of other objects.  The convention followed will be,
// if the object is returning a reference to a Cost you shouldn't modify, the
// method will be called getFoo(), if it's returning a newly-created Cost that
// you can modify, it will be called computeFoo().  Why, oh why can't Java
// implement C++'s const keyword?  I sometimes want to return a const Cost&.

import java.text.*;

public class Cost implements Comparable {

        public int compareTo(Object other) {

// this println is for testing purposes to see how many comparisons are made
// durnig various stages of the main loop, it should be commented out later.
//System.out.println("\t(" + toString() + ").compareTo(" + ((Cost)other).toString() + ")");

// this is for performance measurement reasons
++comparisonCounter;

                if(time < ((Cost)other).time) return -1;
                else if(time == ((Cost)other).time) return 0;
                return 1;
        }

        public Cost() {
                time = 0;
        }

        public Cost(double time) {
                this.time = time;
        }

        // or i could figure out how Cloneable works, but this is quicker
        // make sure this method copies all member variables
        public Cost(Cost cost) {
                time = cost.time;
        }

        // increment myself by other
        public void add(Cost other) {
                // this can be left out for performance, but it is important that nothing changes zero
                if(this == ZERO) throw new IllegalArgumentException("Quit trying to redefine 0!");
                time += other.time;
        }

        // returns a new cost which is the sum of a and b
        public static Cost add(Cost a, Cost b) {
                Cost ret = new Cost();
                ret.time = a.time + b.time;
                return ret;
        }

        public double getTime() {
                return time;
        }

        public String toString() { return twoPlaces.format(time); }

        // how long it took, in seconds
        private double time;

        //this is kinda a hack. Have to know which phyiscal node got onto bus
        //this is only used by BusNode!!!
        public Node physicalNodeGotOntoBus;

        // this is a constant cost, so that when you need a cost to be zero,
        // you needn't create an object.  Changing it should raise an exception,
        // so don't try.
        public static final Cost ZERO = new Cost(0);

        // so we can print without being ugly
        private static final DecimalFormat twoPlaces = new DecimalFormat("0.##");

        // for performance benchmarking
        public static int comparisonCounter;
}