java ducktype class

DuckType.java

/*
class Duck {
	public void quack() { System.out.println("quack"); }
}

interface Quacker {
	public void quack();
}

{
	Object duck = new Duck();
	
	Quacker quacker = DuckType.to(duck, Quacker.class);
	quacker.quack();
}
*/

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class DuckType {
	private static class CoercedProxy implements InvocationHandler {
		private final Object object;

		public CoercedProxy(Object object) {
			this.object = object;
		}

		public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
			return object.getClass()
					.getMethod(method.getName(), method.getParameterTypes())
					.invoke(object, args);
		}
	}

	public static <T> T to(Object object, Class<T> iface) {
		assert iface.isInterface() : "cannot coerce object to a class, must be an interface";
		if (object.getClass().isInstance(iface)) {
			return iface.cast(object);
		}
		for (Method method : iface.getMethods()) {
			try {
				object.getClass().getMethod(method.getName(), method.getParameterTypes());
			} catch (NoSuchMethodException e) {
				throw new ClassCastException("Could not coerce object of type " + object.getClass() + " to " + iface);
			}
		}
		return (T) Proxy.newProxyInstance(iface.getClassLoader(), new Class[]{iface}, new CoercedProxy(object));
	}
}