In reply to burra thanuja:
module abc;
class aa;
rand int unsigned val[10];
constraint s1 {
foreach(val[i]){
val[i] < 10;
foreach(val[j]){
if(i != j)
val[i] != val[j];
}
}
}
endclass
initial begin
aa a1 = new();
a1.randomize();
$display(a1.val);
end
endmodule
this is the way to generate the unique values with out using unique keyword