import org.coinor.opents.*;public class MyObjectiveFunction implements ObjectiveFunction{    public double[][] matrix;            public MyObjectiveFunction( double[][] customers )     {   matrix = createMatrix( customers );    }   // end constructor        public double[] evaluate( Solution solution, Move move )    {        int[] tour = ((MySolution)solution).tour;        int len = tour.length;                // If move is null, calculate distance from scratch        if( move == null )        {            double dist = 0;            for( int i = 0; i < len; i++ )                dist += matrix[ tour[i] ][ i+1 >= len ? 0 : tour[i+1] ];                            return new double[]{ dist };        }   // end if: move == null        // Else calculate incrementally        else        {            MySwapMove mv = (MySwapMove)move;            int pos1 = -1;            int pos2 = -1;                        // Find positions            for( int i = 0; i < tour.length; i++ )                if( tour[i] == mv.customer ) {                       pos1 = i;                    break;                }            pos2 = pos1 + mv.movement;                        // Logic below requires pos1 < pos2            if( pos1 > pos2 )            {                int temp = pos2;                pos2 = pos1;                pos1 = temp;            }   // end if                        // Prior objective value            double dist = solution.getObjectiveValue()[0];                        // Treat a pair swap move differently            if( pos1 + 1 == pos2 )            {   
                //     | |                // A-B-C-D-E: swap C and D, say (works for symmetric matrix only)
                dist -= matrix[ tour[pos1-1] ][ tour[pos1] ];           // -BC
                dist -= matrix[ tour[pos2]   ][ tour[(pos2+1)%len] ];   // -DE
                dist += matrix[ tour[pos1-1] ][ tour[pos2] ];           // +BD
                dist += matrix[ tour[pos1]   ][ tour[(pos2+1)%len] ];   // +CE                return new double[]{ dist };            }   // end if: pair swap                        // Else the swap is separated by at least one customer            else            {   
                //   |     |                // A-B-C-D-E-F: swap B and E, say                dist -= matrix[ tour[pos1-1] ][ tour[pos1] ];           // -AB                dist -= matrix[ tour[pos1]   ][ tour[pos1+1] ];         // -BC                dist -= matrix[ tour[pos2-1] ][ tour[pos2] ];           // -DE                dist -= matrix[ tour[pos2]   ][ tour[(pos2+1)%len] ];   // -EF                                dist += matrix[ tour[pos1-1] ][ tour[pos2] ];           // +AE                dist += matrix[ tour[pos2]   ][ tour[pos1+1] ];         // +EC                dist += matrix[ tour[pos2-1] ][ tour[pos1] ];           // +DB                dist += matrix[ tour[pos1]   ][ tour[(pos2+1)%len] ];   // +BF                return new double[]{ dist };            }   // end else: not a pair swap        }   // end else: calculate incremental    }   // end evaluate            /** Create symmetric matrix. */    private double[][] createMatrix( double[][] customers )    {        int len = customers.length;        double[][] matrix = new double[len][len];                for( int i = 0; i < len; i++ )            for( int j = i+1; j < len; j++ )                matrix[i][j] = matrix[j][i] = norm(                    customers[i][0], customers[i][1],                    customers[j][0], customers[j][1] );        return matrix;    }   // end createMatrix            /** Calculate distance between two points. */    private double norm( double x1, double y1, double x2, double y2 )    {           double xDiff = x2 - x1;        double yDiff = y2 - y1;        return Math.sqrt( xDiff*xDiff + yDiff*yDiff );    }   // end norm    }   // end class MyObjectiveFunction