10. class Foo { 11. static void alpha() { /* more code here */ } 12. void beta() { /* more code here */ } 13. } Which two are true?()
第1题:
现有包结构: com |-- x | |-- Alpha.class | | | |-- y | |-- Beta.class | |-- Gamma.class 和类: //insert code here import com.*; import com.x.y.*; class Test { Alpha a; Beta b; Gamma c; } 哪两行分别插入后可允许代码编译?()
第2题:
1. public class A { 2. public void method1() { 3. B b=new B(); 4. b.method2(); 5. // more code here 6. } 7. } 1. public class B { 2. public void method2() { 3.C c=new C(); 4. c.method3(); 5. // more code here 6. } 7. } 1. public class C { 2. public void method3() { 3. // more code here 4. } 5. } Given: 25. try { 26. A a=new A(); 27. a.method1(); 28. } catch (Exception e) { 29. System.out.print(”an error occurred”); 30. } Which two are true if a NullPointerException is thrown on line 3 of class C?()
第3题:
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 */ }
第4题:
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?()
第5题:
public class Team extends java.util.LinkedList { public void addPlayer(Player p) { add(p); } public void compete(Team opponent) { /* more code here */ } } class Player { /* more code here */ } Which two are true?()
第6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?()
第7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?()
第8题:
A.Alpha a = x;
B.Foo f = (Delta)x;
C.Foo f = (Alpha)x;
D.Beta b = (Beta)(Alpha)x;
第9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?()
第10题:
interface Beta {} class Alpha implements Beta { String testIt() { return “Tested”; } } public class Main1 { static Beta getIt() { return new Alpha(); } public static void main( String[] args ) { Beta b = getIt(); System.out.println( b.testIt() ); } } What is the result?()