import java.util.Scanner; // bring in Scanner class so we can use it

public class While
  /** This class Introduces While Loop **/
  // loop tells jvm to execute statements repeatedly
{
  public static void main(String[] args)
  {  
    /* general format of a while loop:
     * 
    while (boolean expr)  {
      
      body of while loop
      
    }**/
    int num=1;
    while (num < 5) {  
      System.out.println("hello world");
      num++;
    }
    
    System.out.println("Counting down:");
    int count=5;
    while (count > 0) {
        System.out.print(count+" ");
        count--; 
    }
     // ask the user how many times 
    Scanner keyboard = new Scanner(System.in);
    System.out.print("\nHow many times should loop run?");
    count = keyboard.nextInt(); // read in count
    
    while (count > 0) {
        System.out.print(count+" ");
        count--; 
    }
  
    System.out.println("\nNew loop, running until a sentinel: ");
    // using a sentinel value
    // and structured read loop
    int number=0; // number will hold the data value we read in
    System.out.print("Enter a number, -1 to exit: ");
    number = keyboard.nextInt();
    while (number != -1) {
         // this while loop will read in numbers, and display them
         // until the user enters a -1
         System.out.println("you entered: " + number);
         // in a structured read loop, the last thing you do
         // is read in value for NEXT iteration of the loop
         System.out.print("Enter a number, -1 to exit: ");
          number = keyboard.nextInt();
    }
  }
}

/**************
  * LAB 7:
  * Write a while loop to read in names. Each time a name is read
  * in, we say hello to that person.
  * When user enters a . (dot) program terminates and prints Good Bye!
  * 
  * sample output:
  * Enter a name: Alice
  * Hello Alice!
  * Enter a name: Bob
  * Hello Bob!
  * .
  * Good bye!
  *****************/
  * 
  * 
  * 
  * 
  * 
  * 
  *