java OOP习题.docx

Question 1A B D Given:11. public interface Status {12. /* insert code here */ int MY_VALUE = 10;13. }Which three are valid on line 12? (Choose three.)A. finalB. staticC. nativeD. publicE. privateF. abstractG. protectedQuestion 2DGiven:11. public class Test {12. public static void main(String [] args) {13. int x =5;14. boolean b1 = true;15. boolean b2 = false;16.17.if((x==4) !b2)18. System.out.print(”l “);19. System.out.print(”2 “);20. if ((b2 = true) b1)21. System.out.print(”3 “);22. }23. }What is the result?A. 2B. 3C. 1 2D. 2 3E. 1 2 3F. Compilation fails.G. Au exceptional is thrown at runtime.Question3B Given: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 here17. }18. }Which code, inserted at line 16, will cause ajava.lang.ClassCastException?A. Alpha a = x;B. Foo f= (Delta)x;C. Foo f= (Alpha)x;D. Beta b = (Beta)(Alpha)x;Question 4CGiven:20. public class CreditCard {21.22. private String cardlD;23. private Integer limit;24. public String ownerName;25.26. public void setCardlnformation(String cardlD,27. String ownerName,28. Integer limit) {29. this.cardlD = cardlD;30. this.ownerName = ownerName;31. this.limit = limit;32. }33. }Which is true?A. The class is fully encapsulated.B. The code demonstrates polymorphism.C. The ownerName variable breaks encapsulation.D. The cardlD and limit variables break polymorphism.E. The setCardlnformation method breaks encapsulation.Question 5B E第12行，编译都过不了Assume that country is set for each class.Given:10. public class Money {11. private String country, name;12. public getCountry() { return country; }13.}and:24. class Yen extends Money {25. public String getCountry() { return super.country; }26. }27.28. class Euro extends Money {29. public String getCountry(String timeZone) {30. return super.getCountry();31. }32. }Which two are correct? (Choose two.)A. Yen returns correct values