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How can you force garbage collection of an object？（）
- A、 Garbage collection cannot be forced.
- B、 Call System.gc（）.
- C、 Call System.gc（）， passing in a reference to the object to be garbage collected.
- D、 Call Runtime.gc（）.
- E、 Set all references to the object to new values（null， for example）.
参考答案
更多 “How can you force garbage collection of an object？（）A、 Garbage collection cannot be forced.B、 Call System.gc（）.C、 Call System.gc（）， passing in a reference to the object to be garbage collected.D、 Call Runtime.gc（）.E、 Set all references to the object to new values（null， for example）.” 相关考题
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public class X { public object m （） { object o = new float （3.14F）； object oa = new object [1]； oa[0]= o； o = null； return oa[0]； } } When is the float object created in line 3， eligible for garbage collection？（）A、 Just after line 5B、 Just after line 6C、 Just after line 7 （that is， as the method returns）D、 Never in this method.
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1. class TestA { 2. TestB b； 3. TestA（） { 4. b = new TestB（this）； 5. } 6. } 7. class TestB { 8. TestA a； 9. TestB（TestA a） { 10. this.a = a； 11. } 12. } 13. class TestAll { 14. public static void main （String args[]） { 15. new TestAll（）.makeThings（）； 16. // ...code continues on 17. } 18. void makeThings（） { 19. TestA test = new TestA（）； 20. } 21. } Which two statements are true after line 15， before main completes？（）A、 Line 15 causes a stack overflow.B、 An exception is thrown at runtime.C、 The object referenced by a is eligible for garbage collection.D、 The object referenced by b is eligible for garbage collection.E、 The object referenced by a is not eligible for garbage collection.F、 The object referenced by b is not eligible for garbage collection.
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What allows the programmer to destroy an object x？（） A、 x.delete（）B、 x.finalize（）C、 Runtime.getRuntime（）.gc（）D、 Explicitly setting the object’s reference to null.E、 Ensuring there are no references to the object.F、 Only the garbage collection system can destroy an object.
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10. public Object m（） { 11. Object o = new Float（3.14F）； 12. Object [] oa = new Object[1]； 13. oa[0] = o； 14. o = null； 15. return oa[0]； 16. } When is the Float object， created in line 11， eligible for garbage collection？（） A、 Just after line 13.B、 Just after line 14.C、 Never in this method.D、 Just after line 15 （that is， as the method returns）.
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12. void start（） { 13. A a = new A（）； 14. B b = new B（）； 15. a.s（b）； 16. b = null； 17. a = null； 18. System.out.println（“start completed”）； 19. } When is the B object， created in line 14， eligible for garbage collection？（） A、 After line 16.B、 After line 17.C、 After line 18 （when the methods ends）.D、 There is no way to be absolutely certain.E、 The object is NOT eligible for garbage collection.
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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.
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Which statement is true about XpauseTarget in Oracle JRockit JVM ？ （）A、 This option is supported by all type of Garbage collection modes.B、 This option is only supported by Generational Garbage Collection mode.C、 This option is only supported by Mark and Sweep Garbage Collection mode.D、 This option is only supported by Dynamic Garbage Collection mode.
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11. public void genNumbers（） { 12. ArrayList numbers = new ArrayList（）； 13. for （int i=0； i10； i++） { 14. int value = i * （（int） Math.random（））； 15. Integer intObj = new Integer（value）； 16. numbers.add（intObj）； 17. } 18. System.out.println（numbers）； 19. } Which line of code marks the earliest point that an object referenced by intObj becomes a candidate for garbage collection？（） A、 Line 16B、 Line 17C、 Line 18D、 Line 19E、 The object is NOT a candidate for garbage collection.
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You have a use case in your web application that adds several session-scoped attributes. At the end of theuse case， one of these objects， the manager attribute， is removed and then it needs to decide which of theother session-scoped attributes to remove. How can this goal be accomplished？（）A、The object of the manager attribute should implement the HttpSessionBindingListener and it should call the removeAttribute method on the appropriate session attributes.B、The object of the manager attribute should implement the HttpSessionListener and it should call the removeAttribute method on the appropriate session attributes.C、The object of the manager attribute should implement the HttpSessionBindingListener and it should call the deleteAttribute method on the appropriate session attributes.D、The object of the manager attribute should implement the HttpSessionListener and it should call the deleteAttribute method on the appropriate session attributes.
考题
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.
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public class X { public object m （） { object o = new float （3.14F）； object oa = new object [1]； oa[0]= o； o = null； oa[0] = null； return o； } } When is the float object created in line 3， eligible for garbage collection？（） A、 Just after line 5.B、 Just after line 6.C、 Just after line 7.D、 Just after line 8（that is， as the method returns）.
考题
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.
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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.
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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 limitB、 garbage collection frequencyC、 garbage collection timesD、 fragmentation heap size
考题
单选题11.class Snoochy{ 12.Boochybooch； 13.public Snoochy（）{booch=newBoochy（this）；} 14.} 15. 16.class Boochy{ 17.Snoochy snooch； 18.public Boochy（Snoochys）{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.
考题
单选题Given： Which line of code marks the earliest point that an object referenced by intObj becomes a candidate for garbage collection？（）A
Line 16B
Line 17C
Line 18D
Line 19
考题
单选题What allows the programmer to destroy an object x？（）A
x.delete（）B
x.finalize（）C
Runtime.getRuntime（）.gc（）D
Explicitly setting the object’s reference to null.E
Ensuring there are no references to the object.F
Only the garbage collection system can destroy an object.
考题
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.
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You have a use case in your web application that adds several session-scoped attributes. At the end of theuse case， one of these objects， the manager attribute， is removed and then it needs to decide which of theother session-scoped attributes to remove. How can this goal be accomplished？（）A
The object of the manager attribute should implement the HttpSessionBindingListener and it should call the removeAttribute method on the appropriate session attributes.B
The object of the manager attribute should implement the HttpSessionListener and it should call the removeAttribute method on the appropriate session attributes.C
The object of the manager attribute should implement the HttpSessionBindingListener and it should call the deleteAttribute method on the appropriate session attributes.D
The object of the manager attribute should implement the HttpSessionListener and it should call the deleteAttribute method on the appropriate session attributes.
考题
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.
考题
多选题1. class TestA { 2. TestB b； 3. TestA（） { 4. b = new TestB（this）； 5. } 6. } 7. class TestB { 8. TestA a； 9. TestB（TestA a） { 10. this.a = a； 11. } 12. } 13. class TestAll { 14. public static void main （String args[]） { 15. new TestAll（）.makeThings（）； 16. // ...code continues on 17. } 18. void makeThings（） { 19. TestA test = new TestA（）； 20. } 21. } Which two statements are true after line 15， before main completes？（）ALine 15 causes a stack overflow.BAn exception is thrown at runtime.CThe object referenced by a is eligible for garbage collection.DThe object referenced by b is eligible for garbage collection.EThe object referenced by a is not eligible for garbage collection.FThe object referenced by b is not eligible for garbage collection.
考题
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？（）AThere are no instanced of A that will become eligible for garbage collection.BExplicitly setting myA to null marks that instance to be eligible for garbage collection.CAny call on tryIt（） causes the private instance of A to be marked for garbage collection.DPrivate instances of A become eligible for garbage collection when instances of Alpha become eligible for garbage collection.
考题
单选题How can you force garbage collection of an object？（）A
Garbage collection cannot be forced.B
Call System.gc（）.C
Call System.gc（）， passing in a reference to the object to be garbage collected.D
Call Runtime.gc（）.E
Set all references to the object to new values（null， for example）.
考题
单选题public class X { public object m （） { object o = new float （3.14F）； object oa = new object [1]； oa[0]= o； o = null； oa[0] = null； return o； } } When is the float object created in line 3， eligible for garbage collection？（）A
Just after line 5.B
Just after line 6.C
Just after line 7.D
Just after line 8（that is， as the method returns）.
考题
单选题Which statement is true about XpauseTarget in Oracle JRockit JVM ？ （）A
This option is supported by all type of Garbage collection modes.B
This option is only supported by Generational Garbage Collection mode.C
This option is only supported by Mark and Sweep Garbage Collection mode.D
This option is only supported by Dynamic Garbage Collection mode.
考题
单选题12. void start（） { 13. A a = new A（）； 14. B b = new B（）； 15. a.s（b）； 16. b = null； 17. a = null； 18. System.out.println（“start completed”）； 19. } When is the B object， created in line 14， eligible for garbage collection？（）A
After line 16.B
After line 17.C
After line 18 （when the methods ends）.D
There is no way to be absolutely certain.E
The object is NOT eligible for garbage collection.
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