FibonacciIterator

FibonacciIterator

public class FibonacciIterator implements Iterator<Integer>{
    private Integer start;
    private Integer end;
    private int number;
    private Integer upperLimit;
    private Integer nextNumber;


    public FibonacciIterator(Integer start, Integer end, Integer upperLimit) {
        if(start<=end && end<=upperLimit){
            this.start = start;
            this.end = end;
            this.upperLimit = upperLimit;
            number=1;
        }else{
            throw new IllegalArgumentException("Invalid input...");
        }
        setAdvance();
    }

    @Override
    public boolean hasNext() {
        return nextNumber<=upperLimit;
    }

    @Override
    public Integer next() {
        if(!hasNext()){
            throw new NoSuchElementException("No More elements");
        }
        int prevNextNumber = nextNumber;
        setAdvance();
        return prevNextNumber;
    }

    private void setAdvance(){
        if(number==1){
            nextNumber = start;
            number++;
        }else if (number==2){
            nextNumber=end;
            number++;
        }else{
            int sum = start+end;
            start=end;
            end=sum;
            nextNumber=end;
        }
    }

}