Generics in java

generics-in-java.md

public class MainClass {

	public static void main(String args[]) {

		Holder<Duck> myDuck = new Holder<Duck>(new Duck());
		myDuck.behaviour();

		Holder<Dog> myDog = new Holder<Dog>(new Dog());
		myDog.behaviour();
		
		//定義する時にまだクラスを分からない場合
		Holder<?> mySpecialAnimal ;
		mySpecialAnimal = new Holder<Duck>(new Duck());

	}

}

//注意： animalはinterfaceなのに、extendsを利用
//interfaceじゃなくてclassでもいけますよ！
class Holder<T extends Animal> {

	private T myAnimal;
	
	//constructor
	public Holder(T animal){
		this.myAnimal=animal;
	}

	//食べる+飲む
	public void behaviour() {
		myAnimal.drink();
		myAnimal.eat();
	}

}

interface Animal {
	public void eat();
	public void drink();
}

class Duck implements Animal {
	public void eat() {
		System.out.println("食べた！(duck)");
	}
	public void drink() {
		System.out.println("飲んだ！(duck)");
	}
}

class Dog implements Animal {
	public void drink() {
		System.out.println("飲んだ！(dog)");
	}
	public void eat() {
		System.out.println("食べた！(dog)");
	}
}