Hanging program; please help

Question

import cs1.Keyboard;
public class Lab3Prog2Stage3 {
   public static void main(String[] args) {
      final int PENNY_VALUE = 1;
      final int NICKEL_VALUE = 5;
      final int DIME_VALUE = 10;
      final int QUARTER_VALUE = 25;
      int penniesAvail;
      int nickelsAvail;
      int dimesAvail;
      int quartersAvail;
      int pennies;
      int nickels;
      int dimes;
      int quarters;
      int penniesFinal;
      int nickelsFinal;
      int dimesFinal;
      int quartersFinal;
      int change;
      do {
         System.out.print("Enter change drawer counts (Q, D, N, P): ");
         quartersAvail = Keyboard.readInt();
         dimesAvail = Keyboard.readInt();
         nickelsAvail = Keyboard.readInt();
         penniesAvail = Keyboard.readInt();
         if (quartersAvail < 0 || dimesAvail < 0 || nickelsAvail < 0 ||
          penniesAvail < 0)
            System.out.println("No negative values allowed");
      while (quartersAvail < 0 || dimesAvail < 0 || nickelsAvail < 0 ||
       penniesAvail < 0);
      System.out.println();
      System.out.print("Enter change to make: ");
      change = Keyboard.readInt();
      while (change < 0) {
         System.out.print("Change must be a nonnegative number: ");
         change = Keyboard.readInt();
      do {
         quarters = 0;
         while (change >= QUARTER_VALUE) {
            quarters++;
            change = change - QUARTER_VALUE;
      while (quarters <= quartersAvail);
      do {
         dimes = 0;
         while (change >= DIME_VALUE) {
            dimes++;
            change = change - DIME_VALUE;
      while (dimes <= dimesAvail);
      do {
         nickels = 0;
         while (change >= NICKEL_VALUE) {
            nickels++;
            change = change - NICKEL_VALUE;
      while (nickels <= nickelsAvail);
      do {
         pennies = 0;
         while (change >= PENNY_VALUE) {
            pennies++;
            change = change - PENNY_VALUE;
      while (pennies <= penniesAvail);
      penniesFinal = penniesAvail - pennies;
      nickelsFinal = nickelsAvail - nickels;
      dimesFinal = dimesAvail - dimes;
      quartersFinal = quartersAvail - quarters;
      System.out.print("Quarters: " + quarters + " Dimes: " + dimes +
       " Nickels: " + nickels + " Pennies: " + pennies);
      System.out.print("Left in drawer: " + quartersFinal + " quarters, " +
       dimesFinal + " dimes, " + nickelsFinal + " nickels and " + penniesFinal
       + " pennies");
}Sample run 1:
Enter change drawer counts (Q, D, N, P): 2 -1 1 20
No negative values allowed
Enter change drawer counts (Q, D, N, P): 2 1 -2 20
No negative values allowed
Enter change drawer counts (Q, D, N, P): 2 1 1 20
Enter change to make: 77
Quarters: 2 Dimes: 1 Nickels: 1 Pennies: 12
Left in drawer: 0 quarters, 0 dimes, 0 nickels and 8 pennies
When I input the change to make, instead of telling me how much of each denomination was used and how much of each denomination I have remaining, the program just hangs idly:
Enter change to make: 77
(nothing)
Might anyone give me some advice as to how to tackle this enigma?

Answer 1

do {
quarters = 0;
while (quartersAvail >= 0) {
while (change >= QUARTER_VALUE) {
quarters++;
change = change - QUARTER_VALUE;
quartersAvail = quartersAvail - 1;
while (quartersAvail >= 0); How come I'm getting negative returns?The issue here is because of you are doing a post-test loop instead of a pre-test loop. In a post-test (like the do/while you are using) the loop is execute once and then continues if the condition is true. Also your spacing makes it a little confusing and many people (like one of the earlier posters) may not realize at first that the while statements are part of the previous do statement instead of a loop to themselves.
ex. post-test
  int i=0;
  do {
    i++;
  } while( false);
  System.out.println(i);  // output should be 1
ex: pre-test
  int i=0;
  while(false) {
    i++;
  System.out.println(i);  // output should be 0