Given: class ClassA {} class ClassB extends ClassA {} class ClassC extends ClassA {} and: ClassA p0 = new ClassA(); ClassB p1 = new ClassB(); ClassC p2 = new ClassC(); ClassA p3 = new ClassB(); ClassA p4 = new ClassC(); Which three are valid?()
下面程序输出的结果为 #include"iostream.h" class A { public: A(){cout<<"CLASSA"<<endl;} ~A() {} }; class B:public A { public: B(){cout<<"CLASSB"<<endl;} ~B() {} }; void main() { A * p; p=new B; B *q; q=new B; }A.CLASS A CLASS BB.CLASS A CLASS B CLASS BC.CLASS A CLASS B CLASS A CLASS BD.CLASS A CLASS B CLASS B CLASS B
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下面程序段的输出结果为( )。 package test; public class ClassA { int x=20: static int y=6; public static void main(String args[]) { ClassB b=new ClassB; go(10); System.out.println("x="+b.x); } } class ClassB { int X; void go(int y) { ClassA a=new ClassA; x=a.Y ; } }A.x=10B.x=20C.x=6D.编译不通过
下面程序输出的结果为 #include"iostream.h” class A { public: A(){cout<<"CLASSA"<<endl;} ~A() {} }; class B:public A { public: B(){cout<<"CLASS B"<<endl;} ~B(){} }; void main() { A*p; p=new B;A.CLASS A CLASS B CLASS B CLASS BB.CLASS A CLASS B CLASS A CLASS BC.CLASS A CLASS B CLASS BD.CLASS A CLASS B
设有以下定义和程序:includeclassA1{public:void show1(){ cout设有以下定义和程序: #include<iostream.h> classA1 { public: void show1() { cout<<"classA1”<<end1; } }; classA2:public A1 { public: void show2() { cout<<"classA2"<<end1; } }; class A3:protected A2 { public: voidshow3() { cout<<"class A1”<<end1; } }; void main() { A1obj1; A2obj2; A3obj3; } 则以下不合语法的调用语句是A.obj1.show1();B.obj2.show1();C.obj3.show1();D.obj2.show2();
下面程序段的输出结果为 package test; public class A { int x=20; static int y=6; public static void main(String args[]) { Class B b=new Class B(); b.go(10); System.out.println(”x=”+b.x); } } class Class B { int x; void go(int y) { ClassA a=new ClassA(); x=a.y; } }A.x=10B.x=20C.x=6D.编译不通过
有以下源程序: package test; public class ClassA { int x=20; static int y=6; public static void main(String args[]) { ClassB b=new ClassB(); b.go(10); System.out.println("x="+b.x); } } class ClassB { int x; void go(int y) { ClassA a=new ClassA(); x=a.y; } } 上述源程序文件的运行结果为( )。A.x=10B.x=20C.x=6D.编译不通过
10. public class ClassA { 11. public void count(int i) { 12. count(++i); 13. } 14. } And: 20. ClassA a = new ClassA(); 21. a.count(3); Which exception or error should be thrown by the virtual machine?() A、 StackOverflowErrorB、 NullPointerExceptionC、 NumberFormatExceptionD、 IllegalArgumentExceptionE、 ExceptionlnlnitializerError