举一反三
- (7-1)定义了Animal类、Cat类和Dog类,则()代码段是正确的。classAnimal{};classCatextendsAnimal{}classDogextendsAnimal{} A: Dog[] a = new Dog[5];a[0] = new Cat(); B: Animal a = new Animal[5];a[0] = new Animal(); C: Dog[]a = new Dog[5];a[0] = new Animal(); D: Cat[]a = new Cat[5];a[0] = new Cat();
- 定义了Animal类、Cat类和Dog类,则()代码段是正确的。classAnimal{};classCatextendsAnimal{ }classDogextendsAnimal{ } A: Dog[ ] ds=new Dog[5];ds[0]=new Animal(); B: Animal[ ] as=new Animal[5];as[0]=new Dog();
- 若Animal是Cat,Dog的父类,则下列选项中,正确的是() A: Animal animal = new Cat(); B: Cat cat = (Cat)new Animal(); C: Animal animal = new Dog(); D: Cat cat = (Cat)new Dog();
- 若Animal是Cat,Dog的父类,则下列选项中,正确的是() A: Animal animal = new Cat(); B: Animal a = new Cat(); Cat cat = (Cat) a; C: Animal animal = new Dog(); D: Cat cat = (Cat)new Dog();
- (7-1)定义了Animal类、Cat类和Dog类,则代码段是正确的。 class Animal{ }; class Cat extends Animal{} class Dog extends Animal{}
内容
- 0
在前面几题的基础上,有子类Dog和Cat继承了父类Animal,如下空格的输出是以下哪个选项?dog = Dog(coco,small); cat = Cat(kawaii)>>> isinstance(dog, Animal)___________>>> isinstance(cat, Animal)___________>>> isinstance(dog, Dog)___________>>> isinstance(dog, Cat)____________
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在前面几题的基础上,有子类Dog和Cat继承了父类Animal,如下空格的输出是以下哪个选项?dog = Dog('coco','small'); cat = Cat('kawaii') >>> isinstance(dog, Animal) ___________ >>> isinstance(cat, Animal) ___________ >>> isinstance(dog, Dog) ___________ >>> isinstance(dog, Cat) ____________ A: True True False False B: True True True False C: True False False True D: True True True True
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请定义一个类Dog,使其继承自Animal类,(注:Dog类没有代码)
- 3
class Animal { public Animal() { System.out.println("Animal!"); } } public class Dog extends Animal{ public Dog() { System.out.println("Dog!"); } public static void main(String[] args) { Dog dog=new Dog(); } }
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下列各种java类的定义,那种是错误的 A: class Animal{}class Dog extends Animal {} B: final class Animal{}class Dog extends Animal{} C: abstract class Animal{}class Dog extends Animal{} D: public class Animal{}class Dog extends Animal{}