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Monday, 23 January 2017

Chapter 24 Exercise 4, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

24.4 (Use the GenericStack class) Write a program that displays the first 50 prime numbers in descending order. Use a stack to store the prime numbers.


public class Exercise04 {

 public static void main(String[] args) {
  int count = 0;
  int number = 2;
  GenericStack<Integer> stack = new GenericStack<>();
  while (count < 50) {
   boolean isPrime = true;
   for (int divisor = 2; divisor <= (int) (Math.sqrt(number)); divisor++) {
    if (number % divisor == 0) {
     isPrime = false;
     break;
    }
   }

   if (isPrime) {
    count++;
    stack.push(number);
   }
   number++;
  }
  while(!stack.isEmpty()) {
   System.out.print(stack.pop() + " ");
  }
 }

 static class GenericStack<E> {
  private java.util.ArrayList<E> list = new java.util.ArrayList<E>();

  public int getSize() {
   return list.size();
  }

  public E peek() {
   return list.get(getSize() - 1);
  }

  public void push(E o) {
   list.add(o);
  }

  public E pop() {
   E o = list.get(getSize() - 1);
   list.remove(getSize() - 1);
   return o;
  }

  public boolean isEmpty() {
   return list.isEmpty();
  }

  @Override
  public String toString() {
   return "stack: " + list.toString();
  }
 }

}

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