// This program demonstrates several new concepts, including:
//   - fencepost loops
//   - String cumulative "sum"
//   - while loops
import java.util.*;

public class LoopPractice {
   public static void main(String[] args) {
      printPowers(2, 7);
      printPowers(10, 5);
      System.out.println();

      printPowers2(2, 7);
      printPowers2(10, 5);
      System.out.println();

      printPowersUntil(2, 100);
      printPowersUntil(10, 100000);
      System.out.println();
      
      Scanner console = new Scanner(System.in);
      System.out.println(sumAll(console));
   }

   // Print out the first num powers of base
   // e.g. 2, 7 -> 2, 4, 8, 16, 32, 64, 128
   //
   // int base - the base of the powers to be printed
   // int num - the number of powers to print
   public static void printPowers(int base, int num) {
      // definite loop
      int power = base;
      System.out.print(power);
      for (int i = 2; i <= num; i++) {
         power *= base;
         System.out.print(", " + power);
      }
      System.out.println();
   }   


   // Print out the first num powers of base
   // e.g. 2, 7 -> 2, 4, 8, 16, 32, 64, 128
   // 
   // This alternate version uses the "last post last" approach.
   //
   // int base - the base of the powers to be printed
   // int num - the number of powers to print
   public static void printPowers2(int base, int num) {
      // definite loop
      int power = base;
      for (int i = 1; i <= num - 1; i++) {
         System.out.print(power + ", ");
         power *= base;
      }
      System.out.println(power);
   }   
   
   // Print out the powers of base up to the first power of base that is 
   //   greater than last
   // e.g. 2, 10 -> 2, 4, 8, 16, 32, 64, 128
   //
   // int base - the base of the powers to be printed
   // int last - the number after which to stop printing powers
   public static void printPowersUntil(int base, int last) {
      // indefinite loop
      int power = base;
      System.out.print(power);    
      while (power < last) {
         System.out.print(", ");    
         power *= base;             
         System.out.print(power); 
      }
      System.out.println();
   }

   // Read in integers from the user until a -1 is typed,
   //   then return the sum of all numbers typed (not including
   //   the -1).
   // 
   // Scanner console - the Scanner to use for input
   public static int sumAll(Scanner console) {
      int total = 0;
      System.out.print("Enter an integer (-1 to stop): ");
      int number = console.nextInt();
      while (number != -1) {
         total += number;
         System.out.print("Enter an integer (-1 to stop): ");
         number = console.nextInt();
      }
      
      return total;
   }   
}