Java Generics 特例

class Animal {
public void test(List<Integer> list) { };
public void test(List<String> list) { };    // compile error
}

class Animal {

}

class Dog extends Animal {

}

class Cat extends Animal {

}

public static void main(String[] args) {
Animal a = new Animal();
Dog b = new Dog();
ArrayList<Animal> la = new ArrayList<Animal>();
ArrayList<Dog> lb = new ArrayList<Dog>();

la = lb; // compile error
lb = la; // compile error

}

refer: http://tutorials.jenkov.com/java-generics/wildcards.html