设计模式 | 工厂方法模式及典型应用

public abstract class Video {
    public abstract void produce();
}

public class JavaVideo extends Video {
    @Override
    public void produce() {
        System.out.println("录制Java课程视频");
    }
}

public class PythonVideo extends Video {
    @Override
    public void produce() {
        System.out.println("录制Python课程视频");
    }
}

public abstract class VideoFactory {
    public abstract Video getVideo();
}

public class JavaVideoFactory extends VideoFactory {
    @Override
    public Video getVideo() {
        return new JavaVideo();
    }
}

public class PythonVideoFactory extends VideoFactory {
    @Override
    public Video getVideo() {
        return new PythonVideo();
    }
}

public class Test {
    public static void main(String[] args) {
        VideoFactory pythonVideoFactory = new PythonVideoFactory();
        VideoFactory javaVideoFactory = new JavaVideoFactory();
        Video pythonVideo = pythonVideoFactory.getVideo();
        pythonVideo.produce();
        Video javaVideo = javaVideoFactory.getVideo();
        javaVideo.produce();
    }
}

录制Python课程视频
录制Java课程视频

public class FEVideo extends Video{
    @Override
    public void produce() {
        System.out.println("录制FE课程视频");
    }
}

public class FEVideoFactory extends VideoFactory{
    @Override
    public Video getVideo() {
        return new FEVideo();
    }
}

public class Test {
    public static void main(String[] args) {
        VideoFactory feVideoFactory = new FEVideoFactory();
        Video feVideo = feVideoFactory.getVideo();
        feVideo.produce();
    }
}

public class Test {
    public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException {
        // 从文件或数据库等外部渠道获取 工厂类名
        String factoryName = "com.designpattern.factorymethod.JavaVideoFactory";
        // 通过反射机制获取工厂类
        Class c = Class.forName(factoryName);
        VideoFactory factory = (VideoFactory)c.newInstance();
        // 生产产品
        Video video = factory.getVideo();
        video.produce();
    }
}

public interface Collection<E> extends Iterable<E> {
    Iterator<E> iterator();
    // ...省略
}

public Iterator<E> iterator() {
    return new Itr();
}

/**
 * An optimized version of AbstractList.Itr
 */
private class Itr implements Iterator<E> {
    int cursor;       // index of next element to return
    int lastRet = -1; // index of last element returned; -1 if no such
    int expectedModCount = modCount;

    Itr() {}

    public boolean hasNext() {
        return cursor != size;
    }

    @SuppressWarnings("unchecked")
    public E next() {
        // ...省略...
    }

    public void remove() {
        // ...省略...
    }

    @Override
    @SuppressWarnings("unchecked")
    public void forEachRemaining(Consumer<? super E> consumer) {
        // ...省略...
    }

    final void checkForComodification() {
        // ...省略...
    }
}

public interface Iterator<E> {
    boolean hasNext();

    E next();

    default void remove() {
        throw new UnsupportedOperationException("remove");
    }

    default void forEachRemaining(Consumer<? super E> action) {
        Objects.requireNonNull(action);
        while (hasNext())
            action.accept(next());
    }
}

public interface URLStreamHandlerFactory {
    /**
     * Creates a new {@code URLStreamHandler} instance with the specified protocol.
     *
     * @param   protocol   the protocol ("{@code ftp}", "{@code http}", "{@code nntp}", etc.).
     * @return  a {@code URLStreamHandler} for the specific protocol.
     * @see     java.net.URLStreamHandler
     */
    URLStreamHandler createURLStreamHandler(String protocol);
}

private static class Factory implements URLStreamHandlerFactory {
    private static String PREFIX = "sun.net.www.protocol";

    private Factory() {
    }

    public URLStreamHandler createURLStreamHandler(String var1) {
        String var2 = PREFIX + "." + var1 + ".Handler";

        try {
            Class var3 = Class.forName(var2);
            return (URLStreamHandler)var3.newInstance();
        } catch (ReflectiveOperationException var4) {
            throw new InternalError("could not load " + var1 + "system protocol handler", var4);
        }
    }
}

public class Handler extends URLStreamHandler {
    protected String proxy;
    protected int proxyPort;

    protected int getDefaultPort() {
        return 80;
    }

    public Handler() {
        this.proxy = null;
        this.proxyPort = -1;
    }

    public Handler(String var1, int var2) {
        this.proxy = var1;
        this.proxyPort = var2;
    }

    protected URLConnection openConnection(URL var1) throws IOException {
        return this.openConnection(var1, (Proxy)null);
    }

    protected URLConnection openConnection(URL var1, Proxy var2) throws IOException {
        return new HttpURLConnection(var1, var2, this);
    }
}