Levy flight function for the Monarch Butterfly Optimization Algorithm

Question

I am implementing the Monarch butterfly optimization algorithm in Java. The levy flight function (which I converted from the matlab code of the original MBO project to java) used to update butterflies in subpopulation 2 generates data outside the range of subpopulation 2. Need help to correct the error. Is this the right equation?

Here is the code

public static double[] levyFlight(int stepSize, int dim) {
    double[] deltaX = new double[dim];
        Random rand = new Random().nextDouble();
    
    for (int i = 0; i < dim; i++) {

        double sum = 0.0;
        
        for (int j = 0; j < stepSize; j++) {

            double fx = (Math.tan(Math.PI * rand));

            sum += fx;

        }
        deltaX[i] = sum;

      }
    return deltaX;      
}

public static void imboupdate() {

        int nbtask = taskNum;
    double alpha = 0.0;
    int stepSize
    double[] deltaX = new double[nbtask];

    
    stepSize = (int) Math.ceil(new Random().nextDouble() * 2 * maxIterations);

    deltaX = levyFlight(stepSize, nbtask);

        for(int j = 0; j<SP2; j++) {
        alpha = maxStep /((currentIteration+1) * (currentIteration+1));

        int[] Land2 = new int [taskNum];
        Random rand = new Random().nextDouble();
               
                for(int k = 0; k<nbtask; k++) {

             if(rand> SelfAdaptiveStrategy && rand > adjustmentRate) {
                int[] selectedButterfly = Subpopulation2.get(j);
                        int value = selectedButterfly[k];

                        **Land2[k] = (int) (value + alpha*(deltaX[k] - 0.5));**

            }
           }
         newPopulation.add(Land2);

    }
}