9．现有：
1． class Top { 2. static int X=l；
3． public Top() { x*=3; ) 4． }
5. class Middle extends Top { 6.public Middle() {x+=l; }
7.public static void main(String [] args) { 8.Middle m=new Middle(); 9.System.out.println (x)j 10. } 11. }
结果是什么？ A. 2 B. 3 C. 4
D．编译失败
10．现有两个文件： 1. package X； 2. public class X {
3. public static void doX() {System.out.print (\ 4. } 和：
1．import x.X; 2. class Find {
3. publiC static void main (String [] args) { 4. X myX=new X(); myX.doX(); 5． X.doX()； 6． x.X.aoX()：
7. x.X myX2=new x.X(); myx2 .doX()； 8． } ’ 9． } 结果为：
A. Find类中第4行出现一个错误，编译失败。 B. Find类第5行出现一个错误，编译失败。 C. Find类第6行出现一个错误，编译失败。 D. doX doX doX doX
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11.现有:
1. class Tree {
2. private static String tree = \
3. String getTree () { return tree; } 4. }
5. class Elm extends Tree {
6. private static String tree = \
7. public static void main (String [] args) { 8. new Elm() .go (new Tree()) ; 9. }
10. void go (Tree t) {
11. String s = t.getTree () +Elm.tree + tree + (new
Elm() .getTree ()) ; 12. System.out.println (s) ;
结果为:
A. elm elm elm elm B. tree elm elm elm C. tree elm elm tree D. tree elm tree elm 12.现有:
1. interface Animal { 2. void eat () ; 3. } 4.
5. //insert code here 6.
7. public class HouseCat extends Feline { 8. public void eat() { } 9. }
和五个申明
abstract class Feline implements Animal { }
abstract class Feline implements Animal { void eat () ; } abstract class Feline implements Animal { public void eat();} abstract class Feline implements Animal { public void eat() {} }
abstract class Feline implements Animal { abstract public void eat();} A. 1 B. 2 C. 3 D.4
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· 13．现有：
1. interface I { void go(); } 2．
3. abstract class A implements I { } 4．
5. class C extends A { 6． void go(){ ) 7. }
结果是什么？ A.代码通过编译
B.由于第1行的错误导致编译失败 C.由于笫3行的错误导致编译失败 D.由于第6行的错误导致编译失败
14．现有：
1. interface Data {public void load();}
2. abstract class Info {public abstract void load();} 下列类定义中正确使用Data和Info的是哪项？
A. public class Employee implements Info extends Data { public void load() {／*do something*／) )
B.public class Employee extends Inf.implements Data{ public void load() {／*do something*／} }
c.public class Empl.yee implements Inf extends Data{ public void Data.1oad() {* do something*／} public void load(){／*do something*／} )
D.public class Employee extends Inf implements Data { public void Data.1oad() {／*do something*／) public void info.1oad(){/*do something*/) )
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15. 下列代码正确的是哪项?
A. public class Session implements Runnable, Clonable{ public void run ();
public Object clone () ; }
B. public class Session extends Runnable, Cloneable { public void run() {/*do something*/} public Object clone() {/*make a copy*/} }
C. public abstract class Session
implements Runnable, Clonable { pu)olic void run() {/*do something*/} public Object clone() {/*make a copy*/} }
D. public class Session
implements Runnable, implements Clonable { public void run() {/*do something*/} public Object clone() {/*make a copy*/} }
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参考答案 1B 2BD 3D 4C 5C 6B 7C 8D 9C 10 D 11 C 12 C 13 D 14 B 15 C
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