Chapter 24 Exercise 13, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

24.13 (Fibonacci number iterator) Define an iterator class named FibonacciIterator for iterating Fibonacci numbers. The constructor takes an argument that specifies the limit of the maximum Fibonacci number. For example, new FibonacciIterator(23302) creates an iterator that iterates Fibonacci numbers less than or equal to 23302 . Write a test program that uses this iterator to display all Fibonacci numbers less than or equal to 100000.

import java.util.Iterator;

public class Exercise13 {
  public static void main(String[] args) {
    Iterator<Integer> iterator = new FibonacciIterator(100000);
    while (iterator.hasNext()) {
      System.out.println(iterator.next());
    }
  }
  
  static class FibonacciIterator implements java.util.Iterator<Integer> {
    private int limit;
    private int current = 1;//-1,1,0,1,1,2,3,5
    private int prev=-1;
    
    public FibonacciIterator(int limit) {
      this.limit = limit;
    }
    
    @Override 
    public Integer next() {
      return current;
    }    
    @Override 
    public boolean hasNext() {
  int temp=current;
  current=current+prev;//-1+1=0
  prev=temp;
      if (current >= limit)
        return false;
      else 
        return true;
    }
    
    @Override 
    public void remove() {
      throw new UnsupportedOperationException
        ("Method not supported");
    }
  }
  
}