Thread: Program of creating and printing a random phone number that takes only 8-9 in first three digits

I am going through a Lewis and Loftus book doing all of the examples, trying to get myself reacquainted with the Java language. I've included the exercise's requirements inside of the [CODE] tags.

I've tried everything from a BUNCH of if statements, to trying to make up the 'area' variable out of three separate characters, but I cannot seem to get it right. How do I go about limiting the output so that there are no 8 or 9s?

import java.util.Random;
 
/* Write an application that creates and prints a random phone number
of the form XXX-XXX-XXXX. Include the dashes in the output. Do not
let the first three digits contain an 8 or 9 (but don’t be more restrictive
than that), and make sure that the second set of three digits is
not greater than 742.*/
 
class Test {
 
  public static void phoneNumber(){
    Random random = new Random();
 
    int area = random.nextInt(900)+100;
    int mid = random.nextInt(643)+100;
    int last = random.nextInt(9000)+1000;
 
    System.out.println(area+"-"+mid+"-"+last);
  }
 
  public static void main(String[] args){
    phoneNumber();
 
   }
  }

I used strings to hold the values, since number data types don't keep track of the zeros very well.

    public static void main (String[] args)
    {
        Random gen = new Random();
        // first 3 digits. Can't contain an 8 or 9
        String areaCode = "";
        for (int i = 0; i < 3; i++)
        {
            areaCode += gen.nextInt(8);
        }
        // second three digits must be less than or equal to 742
        String second = "" + gen.nextInt(743);
        while (second.length() < 3)
        {
            second = "0" + second;
        }
        // last 4 can be anything
        String last = "" + gen.nextInt(10000);
        while (last.length() < 4)
        {
            last = "0" + last;
        }
        System.out.printf(areaCode + "-" + second + "-" + last);
    }