利用泛型接口实现生成器

生成器是一种专门负责创建对象的类，实际上这是工厂方法设计模式的一种应用， 当时用生成器创建对象时，它不需要任何参数，而工厂方法一般需要参数。

import java.util.Iterator;
import java.util.Random;

//一般来说一个生成器只定义一个方法，该方法用以产生新的对象
interface Generator<T> {
	public T next();
}

//一个继承体系
class Coffee {
	private static long counter = 0;
	private final long id = counter++;
	
	@Override
	public String toString() {
		return getClass().getName() + " " + id;
	}
}
class Latte extends Coffee{}
class Macha extends Coffee{}
class Breve extends Coffee{}


//生成器类
public class CoffeeGenerator implements Generator<Coffee>, Iterable<Coffee>{
	
	private int size;
	private Class[] types = {Latte.class, Macha.class, Breve.class};
	private static Random random = new Random(47);
	
	public CoffeeGenerator() {}
	public CoffeeGenerator(int size) {
		this.size = size;
	}
	
	//实现Iterable 重写Iterator方法，是的我们可以利用foreach语法访问
	class CoffeeIterator implements Iterator<Coffee> {
		int count = size;
		@Override
		public boolean hasNext() {
			return count > 0;
		}

		@Override
		public Coffee next() {
			count--;
			return CoffeeGenerator.this.next();
		}

		@Override
		public void remove() {
			// TODO Auto-generated method stub
			
		}
	}
	
	@Override
	public Iterator<Coffee> iterator() {
		// TODO Auto-generated method stub
		return new CoffeeIterator();
	}

	
	//重写生成器的next方法
	@Override
	public Coffee next() {
		Coffee result = null;
		try {
			result = (Coffee)types[random.nextInt(types.length)].newInstance(); //利用Class对象随机生成Coffee对象
		} catch (InstantiationException | IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return result;
	}
	
	public static void main(String[] args) {
		CoffeeGenerator generator = new CoffeeGenerator();
		
		for (int i = 0; i < 5; ++i) {
			System.out.println(generator.next());
		}
				
		System.out.println("------------分割---------------");
		
		for (Coffee c : new CoffeeGenerator(5)) {
			System.out.println(c);
		}
	}
}

输出：
Breve 0
Breve 1
Macha 2
Breve 3
Macha 4
------------分割---------------
Breve 5
Macha 6
Breve 7
Latte 8
Macha 9