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单选题
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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更多 “单选题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；” 相关考题
考题
单选题A programmer has an algorithm that requires a java.util.List that provides an efficient implementation of add（0，object）， but does NOT need to support quick random access. What supports these requirements？（）A
java.util.QueueB
java.util.ArrayListC
java.util.LinearListD
java.util.LinkedList
考题
单选题public class Test { public static void main（String Args[]） { int i =1， j = 0； switch（i） { case 2： j +=6； case 4： j +=1； default： j +=2； case 0： j +=4； } System.out.println（“j =” +j）； } } What is the result？ （）A
0B
2C
4D
6E
9F
13
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单选题Which statement is true for the class java.util.HashSet？ （）A
The elements in the collection are ordered.B
The collection is guaranteed to be immutable.C
The elements in the collection are guaranteed to be unique.D
The elements in the collection are accessed using a unique key.E
The elements in the collections are guaranteed to be synchronized.
考题
单选题public class Test { public static void main（String[] args） { int x = 0； assert （x 0）： “assertion failed”； System.out.println（“finished”）； } } What is the result？（）A
finishedB
Compilation fails.C
An AssertionError is thrown.D
An AssertionError is thrown and finished is output.
考题
多选题Which two are true about has-a and is-a relationships？（）AInheritance represents an is-a relationship.BInheritance represents a has-a relationship.CInterfaces must be used when creating a has-a relationship.DInstance variables can be used when creating a has-a relationship.
考题
单选题Which can be used to decode charS for output？（）A
Java.io.InputStream.B
Java.io.EncodedReader.C
Java.io.InputStreamReader.D
Java.io.InputStreamWriter.E
Java.io.BufferedInputStream.
考题
单选题public static void main（String[] args） { for （int i=0；i6） break； } System.out.println（i）； } What is the result？（）A
6B
7C
10D
11E
Compilation fails.F
An exception is thrown at runtime.
考题
填空题What is the name of the method that threads can use to pause their execution until signalled to continue by another thread？ （） Fill in the name of the method （do not include a parameter list）.
考题
单选题public class Foo implements Runnable （ public void run （Thread t） { system.out.printIn（“Running.”）； } public static void main （String args） { new thread （new Foo（））.start（）； } ） What is the result？（）A
An exception is thrown.B
The program exists without printing anything.C
An error at line 1 causes compilation to fail.D
An error at line 6 causes the compilation to fail.E
“Running” is printed and the program exits.
考题
多选题public class Threads2 implements Runnable { public void nun（） { System.out.println（”run.”）； throw new RuntimeException（”Problem”）； } public static void main（String[] args） { Thread t = new Thread（new Threads2（））； t.start（）； System.out.println（”End of method.”）； } } Which two can be results？（）Ajava.lang.RuntimeException： ProblemBrun. java.lang.RuntimeException： ProblemCEnd of method. java.lang.RuntimeException： ProblemDEnd of method. run.java.lang.RuntimeException： ProblemErun. java.lang.RuntimeException： Problem End of method.
考题
单选题11. static classA { 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.A a=new B（）； 19. a.process（）； 20.} What is the result？（）A
BB
The code runs with no output.C
An exception is thrown at runtime.D
Compilation fails because of an error in line 15.E
Compilation fails because of an error in line 18.F
Compilation fails because of an error in line 19.
考题
多选题public class X { public X aMethod（） { return this；} } public class Y extends X { } Which two methods can be added to the definition of class Y？（）Apublic void aMethod（） {}Bprivate void aMethod（） {}Cpublic void aMethod（String s） {}Dprivate Y aMethod（） { return null； }Epublic X aMethod（） { return new Y（）； }
考题
多选题Which statements describe guaranteed behavior of the garbage collection and finalization mechanisms？（）AObjects are deleted when they can no longer be accessed through any reference.BThe finalize（） method will eventually be called on every object.CThe finalize（） method will never be called more than once on an object.DAn object will not be garbage collected as long as it is possible for an active part of the program to access it through a reference.EThe garbage collector will use a mark and sweep algorithm.
考题
单选题class ClassA { public int numberOfinstances； protected ClassA（int numberOfinstances） { this.numberOflnstances = numberOfinstances； } } public class ExtendedA extends ClassA { private ExtendedA（int numberOfinstances） { super（numberOflnstances）； } public static void main（String[] args） { ExtendedA ext = new ExtendedA（420）； System.out.print（ext.numberOflnstances）； } } Which is true？（）A
420 is the output.B
An exception is thrown at runtime.C
All constructors must be declared public.D
Constructors CANNOT use the private modifier.E
Constructors CANNOT use the protected modifier.
考题
单选题A class games.cards.Poker is correctly defined in the jar file Poker.jar. A user wants to execute the main method of Poker on a UNIX system using the command： java games.cards.Poker What allows the user to do this？（）A
put Poker.jar in directory /stuff/java， and set the CLASSPATH to include /stuff/javaB
put Poker.jar in directory /stuff/java， and set the CLASSPATH to include /stuff/java/*.jarC
Put Poker.jar in directory /stuff/java， and set the CLASSPATH to include /stuff/java/Poker.jarD
put Poker.jar in directory /stuff/java/games/cards， and set the CLASSPATH to include /stuff/javaE
put Poker.jar in directory /stuff/java/games/cards， and set the CLASSPATH to include /stuffijava/*.jarF
put Poker.jar in directory /stuff/java/games/cards， and set the CLASSPATH to include /stuff/java/Poker.jar
考题
单选题1. abstract class AbstractIt { 2. abstract float getFloat（）； 3. } 4. public class AbstractTest extends AbstractIt { 5. private float f1 = 1.0f； 6. private float getFloat（） { return f1； } 7. } What is the result？（）A
Compilation succeeds.B
An exception is thrown.C
Compilation fails because of an error at line 2.D
Compilation fails because of an error at line 6.
考题
单选题11. public void testIfA（） { 12. if（testIfB（”True”）） { 13. System.out.println（”True”）； 14. } else { 15. System.out.println（”Not true”）； 16. } 17. } 18. public Boolean testIfB（String str） { 19. return Boolean.valueOf（str）； 20. } What is the result when method testIfA is invoked？（）A
TrueB
Not trueC
An exception is thrown at runtime.D
Compilation fails because of an error at line 12.E
Compilation fails because of an error at line 19.
考题
多选题Which statements are true concerning the default layout manager for containers in the java.awt package？（）AObjects instantiated from Panel do not have a default layout manager.BObjects instantiated from Panel have FlowLayout as default layout manager.CObjects instantiated from Applet have BorderLayout as default layout manager.DObjects instantiated from Dialog have BorderLayout as default layout manager.EObjects instantiated from Window have the same default layout manager as instances of Applet.
考题
单选题Which code determines the int value foo closest to a double value bar？（）A
Int foo = （int） Math.max（bar）；B
Int foo = （int） Math.min（bar）；C
Int foo = （int） Math.abs（bar）；D
Int foo = （int） Math.ceil（bar）；E
Int foo = （int） Math.floor（bar）；F
Int foo = （int） Math.round（bar）；
考题
多选题public class Parent { public int addValue（ int a， int b） { int s； s = a+b； return s； } } class Child extends Parent { } Which methods can be added into class Child？（）Aint addValue（ int a， int b ）{// do something...}Bpublic void addValue （）{// do something...}Cpublic int addValue（ int a ）{// do something...}Dpublic int addValue（ int a， int b ）throws MyException {//do something...}
考题
单选题Given the following code fragment： 1） String str = null； 2） if （（str != null） （str.length（） 10）） { 3） System.out.println（"more than 10"）； 4） } 5） else if （（str != null） （str.length（） 5）） { 6） System.out.println（"less than 5"）； 7） } 8） else { System.out.println（"end"）； } Which line will cause error？（）A
line 1B
line 2C
line 5D
line 8
考题
单选题1. class A implements Runnable ( 2. int i; 3. public void run （ ） ( 4. try ( 5. thread.sleep(5000); 6. i= 10; 7. ) catch(InterruptedException e) {} 8. ) 9. ) 10. 11. public class Test { 12. public static void main (string args[]) ( 13. try ( 14. A a = new A （ ）; 15. Thread t = new Thread (a); 16. t.start（ ）; 17. 18. int j= a.i; 19. 20. ) catch (Exception e) {} 21. ) 22. } Which statement al line 17 will ensure that j=10 at line 19？（）A
a.wait（）；B
t.wait（）；C
t.join（）；D
t.yield（）；E
t.notify（）；F
a.notify（）；G
t.interrupt（）；
考题
单选题Given a class Repetition： 1. package utils； 2. 3. public class Repetition { 4. public static String twice（String s） { return s + s； } 5. } and given another class Demo： 1. // insert code here 2. 3. public class Demo { 4. public static void main（String[] args） { 5. System.out.println（twice（”pizza”））； 6. } 7. } Which code should be inserted at line 1 of Demo.java to compile and run Demo to print“pizzapizza”？（）A
import utils.*；B
static import utils.*；C
import utils.Repetition.*；D
static import utils.Repetition. *；E
import utils.Repetition.twice（）；F
import static utils.Repetition.twice；G
static import utils.Repetition.twice；
考题
多选题public class Parent { int change（） {…} } class Child extends Parent { } Which methods can be added into class Child？（）Apublic int change（）{}Bint chang（int i）{}Cprivate int change（）{}Dabstract int chang（）{}
考题
单选题What will be written to the standard output when the following program is run？（） public class Qd803 { public static void main（String args[]） { String word = "restructure"； System.out.println（word.substring（2， 3））； } }A
estB
esC
strD
stE
s
考题
单选题Which statement is true？（）A
If only one thread is blocked in the wait method of an object， and another thread executes the modify on that same object， then the first thread immediately resumes execution.B
If a thread is blocked in the wait method of an object， and another thread executes the notify method on the same object， it is still possible that the first thread might never resume execution.C
If a thread is blocked in the wait method of an object， and another thread executes the notify method on the same object， then the first thread definitely resumes execution as a direct and sole consequence of the notify call.D
If two threads are blocked in the wait method of one object， and another thread executes the notify method on the same object， then the first thread that executed the wait call first definitely resumes execution as a direct and sole consequence of the notify call.
考题
单选题ClassOne.java： 1. package com.abe.pkg1； 2. public class ClassOne { 3. private char var = ‘a’； 4. char getVar（） { return var； } 5. } ClassTest.java： 1. package com.abe.pkg2； 2. import com.abc.pkg1.ClassOne； 3. public class ClassTest extends ClassOne { 4. public static void main（String[] args） { 5. char a = new ClassOne（）.getVar（）；6. char b = new ClassTest（）.getVar（）； 7. } 8. } What is the result？（）A
Compilation fails.B
Compilation succeeds and no exceptions are thrown.C
An exception is thrown at line 5 in ClassTest.java.D
An exception is thrown at line 6 in ClassTest.java.
考题
单选题interface Data { public void load（）； } abstract class Info { public abstract void load（）； } Which class correctly uses the Data interface and Info class？（）A
public class Employee extends Info implements Data { public void load（） { /*do something*/ } }B
public class Employee implements Info extends Data { public void load（） { /*do something*/ } }C
public class Employee extends Info implements Data { public void load（） { /*do something */ } public void Info.load（） { /*do something*/ } }D
public class Employee implements Info extends Data { public void Data.load（） { /*dsomething */ } public void load（） { /*do something */ } }E
public class Employee implements Info extends Data { public void load（） { /*do something */ } public void Info.load（）{ /*do something*/ } }F
public class Employee extends Info implements Data{ public void Data.load（） { /*do something*/ } public void Info.load（） { /*do something*/ } }
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