//WhileLoopsDemo.java

import java.awt.*;
import javax.swing.*;

public class WhileLoopsDemo extends JApplet {    

    public void static main(String[] argv) {
     //public void init() {
	String input;
	int n;
	double num;

	//Loop until the user wants to stop.  
	//does not ask up front how many numbers.
	//A particular value ("sentinel") will be used to indicate the end of input.
	//while loop is better than for loop for this "indefinite iteration".
	//Use for loop when know how many times to loop: "N" times.

	//"priming read" to get first number:
	input = JOptionPane.showInputDialog("Enter number for square rooting" +
                                       " (0 to quit)");
	num = Double.parseDouble( input );
	
	while (num != 0) {    //0 will be "sentinel" that indicates end of input
	    if (num > 0)
		JOptionPane.showMessageDialog(null, "square root is " + 
					      Math.sqrt(num) ); 	
	    else
		JOptionPane.showMessageDialog(null, "No square root of negative number" ); 	
	    
	    //get next number (at bottom of loop, typically)
	    input = JOptionPane.showInputDialog( "Enter a number for square rooting" +
                                       " (0 to quit)");
	    num = Double.parseDouble( input );
	}

	//**************************************************	
	//"error-checking/data validation loop" to ensure valid input
	//Note that these booleanExpressions are the same examples from our if examples.
	input = JOptionPane.showInputDialog("Enter a number between 1 and 5");
	n = Integer.parseInt( input );
	while (n<1 || n>5) {    // while bad input
	    input = JOptionPane.showInputDialog( "Invalid." +
						 "Must be between 1 and 5\n" +
					   "Enter a number between 1 and 5" );
	    n = Integer.parseInt( input );
	}
	//after the loop, the num is valid, ie. between 1 and 5...
	JOptionPane.showMessageDialog(null, "Thanks for " + n ); 	

	//**************************************************	
	input = JOptionPane.showInputDialog( "Enter: 1, 5, or 8" );
	n = Integer.parseInt( input );
	while (n!=1 && n!= 5 && n!=8) {   //while not 1 AND not 5 AND not 8
	    input = JOptionPane.showInputDialog("Invalid. Must be 1 or 5 or 8\n" +
						 "Enter 1, 5 or 8" );
	    n = Integer.parseInt( input );
	}
	//after the loop, the num is valid, ie. 1, 5 or 8...
	JOptionPane.showMessageDialog(null, "Thanks for " + n ); 	
	
	//**************************************************	
	String name;
	name = JOptionPane.showInputDialog( "Enter choice: Bob or Jane" );

	while (!name.equalsIgnoreCase("bob") && !name.equalsIgnoreCase("jane"))
		name = JOptionPane.showInputDialog( "Invalid.  Must be Bob or Jane\n" +
						"Enter again:" );
	
	JOptionPane.showMessageDialog(null, "Thanks for " + name ); 	

        //***********************************************
        int i=0;
        while (true) {  //infinite loop
      	    System.out.println("i= " +i);
      	    i++;
        }
    }
} 
/* no braces on bob...
   ; after bob...
   
  show problems if  while (n!=1 ||
*/