In reply to sruthikrapa:
Try this
class address;
int N = 16;
int memRange = 'h1000;
int memLimit = 'h400_0000;
rand bit [26:0] addrs[];
function new;
addrs = new[N];
endfunction
constraint c{
foreach(addrs[S]) if (S != N-1)
addrs[S] + memRange < addrs[S+1];
else
addrs[S] + memRange < memLimit;
}
endclass