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();
A: Dog[ ] ds=new Dog[5];ds[0]=new Animal();
B: Animal[ ] as=new Animal[5];as[0]=new Dog();
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();
- 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();
- 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?
- (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{}