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();
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();
A,B,C
举一反三
- 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();
- (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();
- 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)____________
- Animal 是抽象类 ,Dog类和Cat类继承了Animal 。Animal dog = new Dog();的写法是否正确?
- 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();
内容
- 0
(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{}
- 1
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
- 2
若Animal 是Cat,Dog的父类,则下列选项中,正确的是()
- 3
创建⼀个⽗类Animal,⼀个⼦类Cat,Animal three = new Cat();不是()? A: 向上转型 B: ⾃动转型 C: 向下转型 D: 隐式转型
- 4
若有父类Animal及其两个子类Cat、Dog,则以下类型转换正确的有( )