迭代器模式——电视遥控器的实现

迭代器模式

题目
电视机遥控器就是一个迭代器的实例，通过它可以实现对电视机频道集合的遍历操作，现有TCL和创维两种品牌电视机，模拟电视机遥控器的实现。以下给出了一种实现方式的UML类图。

类图

【分析】
图中Television是抽象聚合类，具体聚合类SkyworthTelevision，其中方法createIterator()创建对应的具体SkyworthIterator对象，具体聚合类TCLTelevision，其中方法createIterator()创建对应的具体TCLIterator对象。TVIterator为抽象迭代器类，具体迭代器类SkyworthIterator和TCLIterator中定义了各自的访问遍历的方法。

界面

相关代码

//抽象聚合类
public interface Television {
	TVIterator createIterator();
}


//具体聚合类
public class TCLTelevision implements Television{
	public Object[] obj={"频道1","频道2","频道3","频道4","频道5"};
	public TVIterator createIterator()
	{
		return new TCLIterator(this);
	}
}


public class SkyworthTelevision implements Television{
	public Object[] obj = {"CCTV-1", "CCTV-2", "CCTV-3", "CCTV-4"};
    public TVIterator createIterator() 
    {
        return new SkyworthIterator(this);
    }
}

//抽象迭代器类
public interface TVIterator {
	void setChannel(int i);
	void next();
	void previous();
	boolean isLast();
	Object currentChannel();
    boolean isFirst();
}


//具体迭代器类
public class TCLIterator implements TVIterator{
	private int currentIndex=0;
	private TCLTelevision tcl;
	public TCLIterator(TCLTelevision tcl) {
		this.tcl=tcl;
	}
		public void next()
		{
			if(currentIndex<tcl.obj.length)
			{
				currentIndex++;
			}
		}
		
		public void previous()
		{
			if(currentIndex>0)
			{
				currentIndex--;
			}
		}	
		
		public void setChannel(int i)
		{
			currentIndex=i;
		}
		
		
		public Object currentChannel()
		{
			return tcl.obj[currentIndex];
		}
		
		public boolean isLast()
		{
			return currentIndex==tcl.obj.length;
		}
		
		public boolean isFirst()
		{
			return currentIndex==0;
		}
}


public class SkyworthIterator implements TVIterator{
	private int currentIndex = 0;
	private SkyworthTelevision skyworth;
	public SkyworthIterator(SkyworthTelevision skyworth) {
		this.skyworth=skyworth;
	}
    public void next() {
        if (currentIndex < skyworth.obj.length) {
            currentIndex++;
        }
    }
    public void previous() {
        if (currentIndex > 0) {
            currentIndex--;
        }
    }

    public void setChannel(int i) {
        if (i >= 0 && i <= skyworth.obj.length) {
            currentIndex = i;
        }
    }

    public Object currentChannel() {
        return skyworth.obj[currentIndex];
    }

    public boolean isFirst() {
        return currentIndex == 0;
    }

    public boolean isLast() {
        return currentIndex == skyworth.obj.length;
    }
}


//客户端
public class Client {
	public static void display(Television tv)
	{
		TVIterator i=tv.createIterator();
		System.out.println("电视机频道：");
		while(!i.isLast())
		{
			System.out.println(i.currentChannel().toString());
			i.next();
		}
	}
	
	public static void main(String[] args) {
        Television tv = new TCLTelevision();

        display(tv);
    }
}

结果