2, the requirement is a Random integer between x and y, namely the specified range, using the Random class nextInt (int n) method,
3, the method to generate (including) from 0 to n (not including) between random integers, is a pseudo-random number, is not really a random number,
4, if x is 0, you need to after random results plus x, the value of the parameter n also need to add 1 minus x, after the last result conforms to the requirements of the scope,
