Iterator Pattern - 행위

👣 문제 상황

자료들을 담고 있는 컨테이너들을 순회하는 방법을
자료구조에 상관없이
공통 인터페이스로 추상화해서 사용하는 패턴.

👣 해결 방법

interface Aggregate {
    Iterator createIterator();
}

interface Iterator {
    boolean hasNext();
    Object next();
}

class ConcreteAggregate implements Aggregate {
    private String[] elements;

    public ConcreteAggregate() {
        elements = new String[]{"A", "B", "C", "D", "E"};
    }

    @Override
    public Iterator createIterator() {
        return new ConcreteIterator(elements);
    }
}

class ConcreteIterator implements Iterator {
    private String[] elements;
    private int position;

    public ConcreteIterator(String[] elements) {
        this.elements = elements;
        position = 0;
    }

    @Override
    public boolean hasNext() {
        return position < elements.length;
    }

    @Override
    public Object next() {
        if (hasNext()) {
            String element = elements[position];
            position++;
            return element;
        }
        return null;
    }
}

public class Main {
    public static void main(String[] args) {
        Aggregate aggregate = new ConcreteAggregate();
        Iterator iterator = aggregate.createIterator();

        while (iterator.hasNext()) {
            String element = (String) iterator.next();
            System.out.println("Element: " + element);
        }
    }
}