There are many complicated ways to move through a TSP solution space, but we will limit ourselves to simple swaps: one customer trades places with another in the lineup.

As before the complete source is available, but we've duplicated it here:

import org.coinor.opents.*;

public class MySwapMove implements Move 
{
    public int customer;
    public int movement;
    
    
    public MySwapMove( int customer, int movement )
    {   
        this.customer = customer;
        this.movement = movement;
    }   // end constructor
    
    
    public void operateOn( Solution soln )
    {
        int[] tour = ((MySolution)soln).tour;
        int   pos1 = -1;
        int   pos2 = -1;
        
        // Find positions
        for( int i = 0; i < tour.length && pos1 < 0; i++ )
            if( tour[i] == customer ) 
                pos1 = i;
        pos2 = pos1 + movement;
        
        // Swap
        int cust2 = tour[pos2];
        tour[pos1] = cust2;
        tour[pos2] = customer;
    }   // end operateOn
    
    
    /** Identify a move for SimpleTabuList */
    public int hashCode()
    {   
        return customer;
    }   // end hashCode
    
}   // end class MySwapMove

The two integers customer and movement define a move such as "Move customer Number Four three places toward the rear." The operateOn(...) method, required by OpenTS, will be called if the move is the chosen one for a given iteration.

Because we're using the SimpleTabuList object that's included in the OpenTS package, we must override the hashCode() method which the SimpleTabuList uses to identify a move. We'll make the hash code equal to the customer number. That means the tabu list will be tracking which customer has moved and will not let a customer move that has moved recently.

That's how we plan to manipulate the solution. Next we'll take a look at how we determine which moves are valid.