make an String Array like
String[] names = {"Sanket", "Kumar", ......};
then in the code
for (int i = 1; i <= number; i++) {
CheckBox ch = new CheckBox(this);
ch.setId((row * 2) + i);
// Replace the line with
//ch.setText(randomString(3));
// with this line
ch.setText(names[i]);
ll.addView(ch);
}