Which statements describe guaranteed behavior of the garbage collection and finalization mechanisms？（）  A、Objects are deleted when they can no longer be accessed through any reference.B、The finalize（） method will eventually be called on every object.C、The

题目

Which statements describe guaranteed behavior of the garbage collection and finalization mechanisms？（）  

  • A、Objects are deleted when they can no longer be accessed through any reference.
  • B、The finalize（） method will eventually be called on every object.
  • C、The finalize（） method will never be called more than once on an object.
  • D、An 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.
  • E、The garbage collector will use a mark and sweep algorithm.
相似考题

1.Which two are true?()A.A finalizer may NOT be invoked explicitly.B.The finalize method declared in class Object takes no action.C.super.finalize（）is called implicitly by any over riding finalize method.D.The finalize method for a given objec twill be called no more than once by the garbage collector.E.The order in which finalize will be called on two objects is based on the order in which the two objects became finalizable.

2.Given:When the doSomething method is called, after which line does the Object created in line 5 become available for garbage collection?()A.Line 5B.Line 6C.Line 7D.Line 8E.Line 9F.Line 10

3. Your web application requires the adding and deleting of many session attributes during a complex usecase. A bug report has come in that indicates that an important session attribute is being deleted too soonand a NullPointerException is being thrown several interactions after the fact. You have decided to create asession event listener that will log when attributes are being deleted so you can track down when theattribute is erroneously being deleted. Which listener class will accomplish this debugging goal？（）A、Create an HttpSessionAttributeListener class and implement the attributeDeleted method and log the attribute name using the getName method on the event object.B、Create an HttpSessionAttributeListener class and implement the attributeRemoved method and log the attribute name using the getName method on the event object.C、Create an SessionAttributeListener class and implement the attributeRemoved method and log the attribute name using the getAttributeName method on the event object.D、Create an SessionAttributeListener class and implement the attributeDeleted method and log the attribute name using the getAttributeName method on the event object.

4.Given a class whose instances, when found in a collection of objects, are sorted by using the compareTo()method, which two statements are true?()A.The class implements java.lang.Comparable.B.The class implements java.util.Comparator.C.The interface used to implement sorting allows this class to define only one sort sequence.D.The interface used to implement sorting allows this class to define many different sort sequences.

更多“Which statements describe guaranteed behavior of the garbage collection and finalization mechanisms？（）  A、Objects are deleted when they can no longer be accessed through any reference.B、The finalize（） method will eventually be called on every object.C、The”相关问题

  • 第1题：

    Which statements concerning the methods notify（） and notifyAll（） are true？  

    • A、Instances of class Thread have a method called notify（）.
    • B、A call to the method notify（） will wake the thread that currently owns the monitor of the object.
    • C、The method notify（） is synchronized.
    • D、The method notifyAll（） is defined in class Thread.
    • E、When there is more than one thread waiting to obtain the monitor of an object， there is no way to be     sure which thread will be notified by the notify（） method.

    正确答案:A,E

  • 第2题：

    Which statement is true for the class java.util.ArrayList？（）  

    • 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.

    正确答案:A

  • 第3题：

    Given a class whose instances， when found in a collection of objects， are sorted by using the compareTo（） method， which two statements are true？（）

    • A、The class implements java.lang.Comparable.
    • B、The class implements java.util.Comparator.
    • C、The interface used to implement sorting allows this class to define only one sort sequence.
    • D、The interface used to implement sorting allows this class to define many different sort sequences.

    正确答案:A,C

  • 第4题：

    Which two statements are true about using the isUserInRole method to implement security in a Java EEapplication？（）

    • A、It can be invoked only from the doGet or doPost methods.
    • B、It can be used independently of the getRemoteUser method.
    • C、Can return "true" even when its argument is NOT defined as a valid role name in the deployment descriptor.
    • D、Using the isUserInRole method overrides any declarative authentication related to the method in which it is invoked.

    正确答案:B,C

  • 第5题：

    class A {  }  class Alpha {  private A myA = new A（）；  void dolt（ A a ） {  a = null；  }  void tryIt（） {  dolt（ myA ）；  }  }  Which two statements are correct？（）  

    • A、 There are no instanced of A that will become eligible for garbage collection.
    • B、 Explicitly setting myA to null marks that instance to be eligible for garbage collection.
    • C、 Any call on tryIt（） causes the private instance of A to be marked for garbage collection.
    • D、 Private instances of A become eligible for garbage collection when instances of Alpha become eligible for garbage collection.

    正确答案:B,D

  • 第6题：

    Oracle JRockit JVM uses -Xns option to set nursery size when the generational garbage collection mode is used.  Which two JVM properties are affected by changing its size ？（）

    • A、 compaction ratio limit
    • B、 garbage collection frequency
    • C、 garbage collection times
    • D、 fragmentation heap size

    正确答案:B,C

  • 第7题：

    Which two statements are true about the hashCode method？（）

    • A、The hashCode method for a given class can be used to test for object equality and object inequality for that class.
    • B、The hashCode method is used by the java.util.SortedSet collection class to order the elements within that set.
    • C、The hashCode method for a given class can be used to test for object inequality， but NOT objecte quality， for that class.
    • D、The only important characteristic of the values returned by a hashCode method is that the distribution of values must follow a Gaussian distribution.
    • E、The hashCode method is used by the java.util.HashSet collection class to group the elements within that set into hash buckets for swift retrieval.

    正确答案:C,E

  • 第8题：

    单选题
    According to the passage, which of the following statements is TRUE?
    A

    The American ship eventually found a port and dumped its garbage before it returned home.

    B

    Throwaway societies don’t need to transport their refuse and garbage to incinerator because they have a lot of space to put them.

    C

    The wandering ship with garbage reflected the fact that garbage problem became very serious.

    D

    The huge populations of rats swarm through poor neighborhood in many Western European countries because the garbage is thrown into the open dumps.


    正确答案： C
    解析：
    C意为“那艘漂泊的船只反映了垃圾问题已很严重了”，与文章第一句话“那艘到处漂泊的船只是一个戏剧性的象征，它突出说明了我们这个时代的一个折磨人的问题：全球垃圾危机。”内容相符。故正确答案为C项。

  • 第9题：

    单选题
    11. class Snoochy {  12. Boochybooch；  13. public Snoochy（） { booch = new Boochy（this）； }  14. }  15.  16. class Boochy {  17. Snoochy snooch；  18. public Boochy（Snoochy s） { snooch = s； }  19. }  And the statements：  21. public static void main（String[] args） {  22. Snoochy snoog = new Snoochy（）；  23. snoog = null；  24. // more code here  25. }  Which statement is true about the objects referenced by snoog， snooch， and booch immediately after line 23 executes？（）
    A

     None of these objects are eligible for garbage collection.

    B

     Only the object referenced by booch is eligible for garbage collection.

    C

     Only the object referenced by snoog is eligible for garbage collection.

    D

     Only the object referenced by snooch is eligible for garbage collection.

    E

     The objects referenced by snooch and booch are eligible for garbage collection.


    正确答案： B
    解析： 暂无解析

  • 第10题：

    单选题
    Given: When the doSomething method is called, after which line does the Object created in line 5 become available for garbage collection?（）
    A

    Line 5

    B

    Line 6

    C

    Line 7

    D

    Line 8

    E

    Line 9

    F

    Line 10


    正确答案： D
    解析： 暂无解析

  • 第11题：

    多选题
    class A {  }  class Alpha {  private A myA = new A（）；  void dolt（ A a ） {  a = null；  }  void tryIt（） {  dolt（ myA ）；  }  }  Which two statements are correct？（）
    A

    There are no instanced of A that will become eligible for garbage collection.

    B

    Explicitly setting myA to null marks that instance to be eligible for garbage collection.

    C

    Any call on tryIt（） causes the private instance of A to be marked for garbage collection.

    D

    Private instances of A become eligible for garbage collection when instances of Alpha become eligible for garbage collection.


    正确答案： A,D
    解析： 暂无解析

  • 第12题：

    多选题
    Which two statements are true about using the isUserInRole method to implement security in a Java EEapplication？（）
    A

    It can be invoked only from the doGet or doPost methods.

    B

    It can be used independently of the getRemoteUser method.

    C

    Can return true even when its argument is NOT defined as a valid role name in the deployment descriptor.

    D

    Using the isUserInRole method overrides any declarative authentication related to the method in which it is invoked.


    正确答案： D,C
    解析： 暂无解析

  • 第13题：

    Which of the following statements about variables and scope are true？（） 

    • A、 Local variables defined inside a method are destroyed when the method is exited.
    • B、 Local variables are also called automatic variables.
    • C、 Variables defined outside a method are created when the object is constructed.
    • D、 A method parameter variable continues to exist for as long as the object is needed in which the method is defined.

    正确答案:A,B,C

  • 第14题：

    Which of the following statements are true？（） 

    • A、 The equals（） method determines if reference values refer to the same object.
    • B、 The == operator determines if the contents and type of two separate objects match.
    • C、 The equals（） method returns true only when the contents of two objects match.
    • D、 The class File overrides equals（） to return true if the contents and type of two separate objects        match.

    正确答案:A,D

  • 第15题：

    Which statements about the garbage collection are true？（） 

    • A、 The program developer must create a thread to be responsible for free the memory.
    • B、 The garbage collection will check for and free memory no longer needed.
    • C、 The garbage collection allow the program developer to explicity and immediately free the memory.
    • D、 The garbage collection can free the memory used java object at expect time.

    正确答案:B

  • 第16题：

    11. class Snoochy {  12. Boochybooch；  13. public Snoochy（） { booch = new Boochy（this）； }  14. }  15.  16. class Boochy {  17. Snoochy snooch；  18. public Boochy（Snoochy s） { snooch = s； }  19. }  And the statements：  21. public static void main（String[] args） {  22. Snoochy snoog = new Snoochy（）；  23. snoog = null；  24. // more code here  25. }  Which statement is true about the objects referenced by snoog， snooch， and booch immediately after line 23 executes？（） 

    • A、 None of these objects are eligible for garbage collection.
    • B、 Only the object referenced by booch is eligible for garbage collection.
    • C、 Only the object referenced by snoog is eligible for garbage collection.
    • D、 Only the object referenced by snooch is eligible for garbage collection.
    • E、 The objects referenced by snooch and booch are eligible for garbage collection.

    正确答案:E

  • 第17题：

    Which statement is true？（）

    • A、A class’s finalize（） method CANNOT be invoked explicitly.
    • B、super.finalize（） is called implicitly by any overriding finalize（） method.
    • C、The finalize（） method for a given object is called no more than once by the garbage collector.
    • D、The order in which finalize（） is called on two objects is based on the order in which the two objects became finalizable.

    正确答案:C

  • 第18题：

    Which three statements are true?（）

    • A、A final method in class X can be abstract if and only if X is abstract.
    • B、A protected method in class X can be overridden by any subclass of X.
    • C、A private static method can be called only within other static methods in class X.
    • D、A non-static public final method in class X can be overridden in any subclass of X.
    • E、A public static method in class X can be called by a subclass of X without explicitly referencing the class X.
    • F、A method with the same signature as a private final method in class X can be implemented in a subclass of X.
    • G、A protected method in class X can be overridden by a subclass of X only if the subclass is in the same package as X.

    正确答案:B,E,F

  • 第19题：

    多选题
    Which of the following statements are true？（）
    A

    The equals（） method determines if reference values refer to the same object.

    B

    The == operator determines if the contents and type of two separate objects match.

    C

    The equals（） method returns true only when the contents of two objects match.

    D

    The class File overrides equals（） to return true if the contents and type of two separate objects        match.


    正确答案： A,D
    解析： 严格来说这个问题的答案是不确定的，因为equals()方法是可以被重载的，但是按照java语言的本意来说：如果没有重写（override）新类的equals()，则该方法和 == 操作符一样在两个变量指向同一对象时返回真，但是java推荐的是使用equals()方法来判断两个对象的内容是否一样，就像String类的equals()方法所做的那样：判定两个String对象的内容是否相同，而==操作符返回true的唯一条件是两个变量指向同一对象。从这个意义上来说选择给定的答案。从更严格的意义来说正确答案应该只有D。

  • 第20题：

    单选题
    Which statement is true？（）
    A

    A class’s finalize（） method CANNOT be invoked explicitly.

    B

    super.finalize（） is called implicitly by any overriding finalize（） method.

    C

    The finalize（） method for a given object is called no more than once by the garbage collector.

    D

    The order in which finalize（） is called on two objects is based on the order in which the two objects became finalizable.


    正确答案： C
    解析： 暂无解析

  • 第21题：

    多选题
    Which statements describe guaranteed behavior of the garbage collection and finalization mechanisms？（）
    A

    Objects are deleted when they can no longer be accessed through any reference.

    B

    The finalize（） method will eventually be called on every object.

    C

    The finalize（） method will never be called more than once on an object.

    D

    An 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.

    E

    The garbage collector will use a mark and sweep algorithm.


    正确答案： B,A
    解析： 暂无解析

  • 第22题：

    单选题
    Which statements about the garbage collection are true？（）
    A

     The program developer must create a thread to be responsible for free the memory.

    B

     The garbage collection will check for and free memory no longer needed.

    C

     The garbage collection allow the program developer to explicity and immediately free the memory.

    D

     The garbage collection can free the memory used java object at expect time.


    正确答案： C
    解析： Java语言将内存分配和释放的工组交给了自己，程序员不必做这些工作，它提供一个系统级的线程跟踪每个内存的分配，在JVM的空闲处理中，垃圾收集线程将检查和释放不再使用的内存（即可以被释放的内存）。垃圾收集的过程在java程序的生存期中是自动的，不需要分配和释放内存，也避免了内存泄漏。可以调用System.gc()方法建议（suggest）JVM执行垃圾收集以使得可被释放的内存能立即被使用，当此方法返回的时候，JVM已经做了最大的努力从被丢弃的对象上回收内存空间。程序员不能指定收集哪些内存，一般而言也不用关心这个问题，除非是程序的内存消耗很大，特别是有很多临时对象时可以“建议“进行垃圾收集以提高可用内存。需要指出的是调用System.gc()方法不能保证JVM立即进行垃圾收集，而只能是建议,因为垃圾收集线程的优先级很低（通常是最低的）。

  • 第23题：

    单选题
    Which statement is true for the class java.util.ArrayList？（）
    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.


    正确答案： C
    解析： 暂无解析

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