What is the purpose of this algorithm, assuming data is a non$-$empty array and both j and k are valid positions in the array?

public void mystery$($int$[]$ data, int j$,$ int k$)$

$\{$

int t $=$ data$[$j$]$;

data$[$j$]=$ data$[$k$]$;

data$[$k$]=$ t;

$\}$