Java设计模式：迭代器模式

快来打我* 2023-11-23 06:18 139阅读 0赞

public interface AbstractIterator<E> {
    	public boolean hasNext();
    	public E next();
    }

import java.util.ArrayList;
    import java.util.List;
    
    public abstract class AbstractObjectList<E> {
    	protected List<E> list = new ArrayList<E>();
    
    	public AbstractObjectList() {
    
    	}
    
    	public AbstractObjectList(List list) {
    		this.list = list;
    	}
    
    	public void add(E e) {
    		this.list.add(e);
    	}
    
    	public E get(int index) {
    		return list.get(index);
    	}
    
    	public int size() {
    		return list.size();
    	}
    
    	public boolean isEmpty() {
    		return list.isEmpty();
    	}
    
    	public abstract AbstractIterator iterator();
    }

import java.util.List;
    
    /**
     * 抽象对象列表的实现。
     * 
     * @author zhangfly
     *
     */
    public class ObjectListImpl extends AbstractObjectList {
    	public ObjectListImpl() {
    
    	}
    
    	public ObjectListImpl(List list) {
    		super(list);
    	}
    
    	@Override
    	public AbstractIterator iterator() {
    		return new IteratorImpl(this);
    	}
    }

/**
     * 迭代器的实现。
     * 
     * @author zhangfly
     *
     * @param <T>
     */
    public class IteratorImpl<E> implements AbstractIterator {
    	private AbstractObjectList<E> list;
    	private int cursor = 0;
    
    	public IteratorImpl(AbstractObjectList list) {
    		this.list = list;
    	}
    
    	@Override
    	public boolean hasNext() {
    		if (list.isEmpty()) {
    			return false;
    		}
    
    		if (cursor < list.size()) {
    			return true;
    		}
    
    		return false;
    	}
    
    	@Override
    	public E next() {
    		E e = null;
    		if (cursor < list.size()) {
    			e = list.get(cursor);
    			cursor++;
    		}
    
    		return e;
    	}
    }

public class Test {
    	public Test() {
    
    		ObjectListImpl listImpl = new ObjectListImpl();
    		
    		// 添加三个不同类型的元素。
    		listImpl.add(new String("zhang"));
    		listImpl.add(new Exception("phil"));
    		listImpl.add(2019);
    
    		// 迭代器遍历。
    		AbstractIterator iterator = listImpl.iterator();
    		while (iterator.hasNext()) {
    			System.out.println(iterator.next().toString());
    		}
    	}
    
    	public static void main(String[] args) {
    		new Test();
    	}
    }

输出：

zhang
    java.lang.Exception: phil
    2019