[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fReouxgt7YJ7_y2J83P0a3odVI6kZrnseVl0CublKE98":3},{"answer":4,"createTime":5,"id":6,"options":7,"origin":12,"question":19,"related":20,"source":30,"type":31},[],"2024-03-31 18:47:34",136426845,[8,9,10,11],"抽象类不能包含抽象方法","接口和抽象类是一回事","抽象类不能实例化,即不能直接调用构造方法生成对象","抽象类可以实例化对象",{"count":13,"courseId":14,"courseImg":15,"courseName":16,"workId":17,"workName":18},15,"8f39179e8e9bd7589885271226eaaa28","https:\u002F\u002Ftihai-oss-cloud.itihey.com\u002Fimg\u002F26feeabf4f7b0cfd6c0f37373ddb1520.jpg","面向对象程序设计(Java)","exam_102570348","单元3测试-类对象","下列关于抽象类的描述正确的是( )",[21,32,35,44,53,62,71,80,89,98],{"answer":22,"createTime":5,"id":23,"options":24,"question":29,"source":30,"type":31},[],136426843,[25,26,27,28],"表达式合法","编译时合法而在运行时可能非法","编译时非法","将构造一个Student对象","类Teacher和Student都是类Person的子类 Person p; Teacher t; Student s; 若p,t和s都是非空值 if(t instanceof Person) { s = (Student)t; } 若默认new时声明的都是本类,这个语句导致的结果是( )","v1",0,{"answer":33,"createTime":5,"id":6,"options":34,"question":19,"source":30,"type":31},[],[8,9,10,11],{"answer":36,"createTime":5,"id":37,"options":38,"question":43,"source":30,"type":31},[],136426846,[39,40,41,42],"一般在创建新对象时,系统会自动调用构造函数","构造函数是类的一种特殊函数,它的方法名必须与类名相同","构造函数的返回类型只能是void型","构造函数的主要作用是完成对类的对象的初始化工作","对于构造函数,下列叙述不正确的是( )",{"answer":45,"createTime":5,"id":46,"options":47,"question":52,"source":30,"type":31},[],136426847,[48,49,50,51],"原来c所指的对象","原来b和c所指的对象","原来a所指的对象","原来b所指的对象","设有Circle类,执行下面语句后,可以被垃圾回收器回收的对象是( ). Circle a=new Circle(); Circle b=new Circle(); Circle c=new Circle(); a = b; a = c; c = null",{"answer":54,"createTime":5,"id":55,"options":56,"question":61,"source":30,"type":31},[],136426848,[57,58,59,60],"static void methoda(){}","final void methoda(){}","static final void methoda(){}","void final methoda(){}","下面方法声明正确但又能被子类重写的是()",{"answer":63,"createTime":5,"id":64,"options":65,"question":70,"source":30,"type":31},[],136426849,[66,67,68,69],"x、y和s都是成员变量","x、y和s都是实例变量","x是实例变量、y是类变量、s是参数","x和y是实例变量、s是参数","参照以下Java代码,以下四个叙述中最确切的是( ) class A{ int x; static int y; void fac(String s){System. out. println("字符串:"+s);} }",{"answer":72,"createTime":5,"id":73,"options":74,"question":79,"source":30,"type":31},[],136426850,[75,76,77,78],"sh和tr分别引用同一类型的不同的对象","sh和tr分别引用不同类型的不同的对象","sh和tr分别引用同一个对象","sh和tr分别引用同一个对象的不同副本","已知Rectangle和Triangle是Shape类的子类,Square是Rectangle的子类.针对下列代码,下面描述正确的是() Triangle tr = new Triangle(); Square sq = new Square(); Shape sh = tr",{"answer":81,"createTime":5,"id":82,"options":83,"question":88,"source":30,"type":31},[],136426851,[84,85,86,87],"Nothing","b is an instance of A followed by b is an instance of C","b is an instance of A","b is an instance of C","根据下列程序代码,选择项描述正确的是() Show the output of running the class Test in the following code lines: interface A { void print(); } class C {} class B extends C implements A { public void print() { } } class Test { public static void main(String[] args) { B b = new B(); if (b instanceof A) System.out.println("b is an instance of A"); if (b instanceof C) System.out.println("b is an instance of C"); } }",{"answer":90,"createTime":5,"id":91,"options":92,"question":97,"source":30,"type":31},[],136426852,[93,94,95,96],"beta gamma","gamma gamma","alpha beta","alpha alpha","下面程序运行结果为(). class Alpha{ String getType(){return "alpha";} } class Beta extends Alpha{ String getType(){return "beta";} } class Gamma extends Beta{ String getType(){return "gamma";} public static void main(String[] args){ Alpha g1=new Beta(); Alpha g2=new Gama(); System.out.println(g1.getType() + "" + g2.getType());} }",{"answer":99,"createTime":5,"id":100,"options":101,"question":106,"source":30,"type":31},[],136426853,[102,103,104,105],"public void getNum(double d){}","public void getNum(){}","public float getNum(){return 4.0f;}","public double getNum(float d){return 4.0d;}","有下面类的定义: Class Super{ Public float getNum(){return 3.0f} } Public class Sub extends Super{ } 下面方法放在画线处会发生编译错误的是( )"]