10. interface Foo {}  11. class Alpha implements Foo {}  12. class Beta extends Alpha {}  13. class Delta extends Beta {  14. public static void main( String[] args) {  15. Beta x = new Beta();  16. // insert code here  17. }  18. }  Which code, inserted 

题目

10. interface Foo {}  11. class Alpha implements Foo {}  12. class Beta extends Alpha {}  13. class Delta extends Beta {  14. public static void main( String[] args) {  15. Beta x = new Beta();  16. // insert code here  17. }  18. }  Which code, inserted at line 16, will cause a java.lang.ClassCastException?() 

  • A、 Alpha a = x;
  • B、 Foo f= (Delta)x;
  • C、 Foo f= (Alpha)x;
  • D、 Beta b = (Beta)(Alpha)x;
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相似问题和答案

第1题:

class One {  void foo() {}  }  class Two extends One {   //insert method here  }  Which three methods, inserted individually at line 14, will correctly complete class Two?()

  • A、 int foo() { /* more code here */ }
  • B、 void foo() { /* more code here */ }
  • C、 public void foo() { /* more code here */ }
  • D、 private void foo() { /* more code here */ }
  • E、 protected void foo() { /* more code here */ }

正确答案:B,C,E

第2题:

10. interface Foo { int bar(); }  11. public class Sprite {  12. public int fubar( Foo foo) { return foo.bar(); }  13. public void testFoo() {  14. fubar(  15. // insert code here  16.);  17. }  18. }  Which code, inserted at line 15, allows the class Sprite to compile?() 

  • A、 Foo { public int bar() { return 1; } }
  • B、 new Foo { public int bar() { return 1; } }
  • C、 newFoo() { public int bar(){return 1; } }
  • D、 new class Foo { public int bar() { return 1; } }

正确答案:C

第3题:

Given:Which code, inserted at line 16, will cause a java.lang.ClassCastException?()

A.Alpha a = x;

B.Foo f = (Delta)x;

C.Foo f = (Alpha)x;

D.Beta b = (Beta)(Alpha)x;


参考答案:B

第4题:

package sun.scjp;  public enum Color { RED, GREEN, BLUE }  package sun.beta;  // insert code here  public class Beta {  Color g = GREEN;  public static void main( String[] argv)  { System.out.println( GREEN); }  }  The class Beta and the enum Color are in different packages.  Which two code fragments, inserted individually at line 2 of the Beta declaration, will allow this code to compile?()

  • A、 import sun.scjp.Color.*;
  • B、 import static sun.scjp.Color.*;
  • C、 import sun.scjp.Color; import static sun.scjp.Color.*;
  • D、 import sun.scjp.*; import static sun.scjp.Color.*;
  • E、 import sun.scjp.Color; import static sun.scjp.Color.GREEN;

正确答案:C,E

第5题:

11. static class A {  12. void process() throws Exception { throw new Exception(); }  13. }  14. static class B extends A {  15. void process() { System.out.println(”B”); }  16. }  17. public static void main(String[] args) {  18. new B().process();  19. }  What is the result?() 

  • A、 B
  • B、 The code runs with no output.
  • C、 Compilation fails because of an error in line 12.
  • D、 Compilation fails because of an error in line 15.
  • E、 Compilation fails because of an error in line 18.

正确答案:A

第6题:

10. class Line {  11. public static class Point { }  12. }  13.  14. class Triangle {  15. // insert code here  16. }  Which code, inserted at line 15, creates an instance of the Point class defined in Line?() 

  • A、 Point p = new Point();
  • B、 Line.Point p = new Line.Point();
  • C、 The Point class cannot be instatiated at line 15.
  • D、 Line 1 = new Line() ; 1.Point p = new 1.Point();

正确答案:B

第7题:

11. public class Counter {  12. public static void main(String[] args) {  13. int numArgs = /* insert code here */;  14. }  15. }  and the command line: java Counter one fred 42 Which code, inserted at line 13, captures the number of arguments passed into the program?() 

  • A、 args.count
  • B、 args.length
  • C、 args.count()
  • D、 args.length()
  • E、 args.getLength()

正确答案:B

第8题:

10. class Foo {  11. static void alpha() { /* more code here */ }  12. void beta() { /* more code here */ }  13. }  Which two are true?()

  • A、 Foo.beta() is a valid invocation of beta().
  • B、 Foo.alpha() is a valid invocation of alpha().
  • C、 Method beta() can directly call method alpha().
  • D、 Method alpha() can directly call method beta().

正确答案:B,C

第9题:

1. class Alpha { void m1() {} }   2. class Beta extends Alpha { void m2() { } }   3. class Gamma extends Beta { }   4.   5. class GreekTest {   6. public static void main(String [] args) {   7. a Alpha [] a = {new Alpha(), new Beta(), new Gamma() };   8. for(Alpha a2 : a) {   9. a2.m1();   10. if (a2 instanceof Beta || a2 instanceof Gamma)   11. //insert code here   12. }   13. }   14. }   哪一行代码插入到第11行,将编译但是会在运行时产生异常?()  

  • A、 a2.m2();
  • B、 ((Beta)a2).m2();
  • C、 ((Alpha)a2).m2();
  • D、 ((Gamma)a2).m2();

正确答案:D

第10题:

10. public class Foo implements java.io.Serializable {  11. private int x;  12. public int getX() { return x; }  12.publicFoo(int x){this.x=x; }  13. private void writeObject( ObjectOutputStream s)  14. throws IOException {  15. // insert code here  16. }  17. }  Which code fragment, inserted at line 15, will allow Foo objects to be correctly serialized and deserialized?() 

  • A、 s.writeInt(x);
  • B、 s.serialize(x);
  • C、 s.writeObject(x);
  • D、 s.defaultWriteObject();

正确答案:D

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