algorithm - Need help completing unfinished implementation of FFT bit reversal in Java -

i'm taking on code meant run fft algorithm on images. fft implementation incomplete , contains following segment:

public complex[] dofft(complex[] data, int size){     complex[] temp = new complex[size];      int j=0;     int k;     for(int i=0; i<size;i++){         temp[i] = data[j];         while((j>=k) && (k>0)){             k /=2;         }         j+=k;     }  ...  } 

where data 1d input array of complex numbers, size length of data , temp output array after of fft algorithm completed. particular block supposed 'bit reversal' step of algorithm.

i've never seen bit reversal done way. k not initialized , have no idea author trying it. i've tried tracing k = 0, k = size, , k = size/2 , none seems give output i'm looking for.

can decipher author trying here or suggest better implementation?