Generate random pairs of numbers, without duplicates

I have to arrays with integers:

int[] a={1,2,3,4,5};
int[] b={6,7};

I would like to generate an array, which contains pairs from the a and b arrays, in a random order, without duplicates. For example I would like to get the following result:

c={(1,6),(2,7),(4,6),...}

Thanks!