题目内容

设有如下代码:
interface IFace{}
class CFace implements IFace{}
class Base{}
public class ObRef extends Base{
public static void main(String argv[]){
ObRef bj = new ObRef();
Base b = new Base();
Object obj1 = new Object();
IFace obj2 = new CFace();
//Here
}
}
则在 //Here处插入哪个代码将不出现编译和运行错误。

A. obj1=obj2;
B. b=obj;
C. obj=b;
D. obj1=b;

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更多问题

试完成下述程序片段:public class Point(){ int x,y;public Point(int x,int y){ =x; =y;}......}

A. Point.x Point.y
B. 无解
C. x1 y1
D. this.x this.y

下列哪个方法不属于播放声音的方法?

A. loop()
B. stop()
C. start()
D. play()

以下程序的调试结果为?class Base{public final void amethod(){System.out.println("amethod");}}public class Fin extends Base{public static void main(String argv[]){Base b = new Base();b.amethod();}}

A. 编译指示带有final 方法的类自己必须定义为final
B. 编译指示不能继承含有final 方法的类
C. 运行错误,原因是Base类没有定义为final类
D. 运行输出 amethod

考虑如下代码:
class Tree{}
class Pine extends Tree{}
class Oak extends Tree{}
public class Forest {
public static void main(String[] args ) {
Tree tree = new Pine();
if(tree instanceof Pine )
System.out.println("Pine" );
if(tree instanceof Tree )
System.out.println("Tree" );
if(tree instanceof Oak )
System.out.println("Oak" );
else
System.out.println("Oops" );
}
}
则输出结果中有哪些?

A. Pine B.Tree C.Forest D.Oops E.无输出

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