corejava interview questions part 6

corejava interview questions part 6

Q - The purpose of garbage collection in Java is to perform all necessary cleanup and the memory

occupied by objects that are no longer needed will always be reclaimed by the garbage collector:

True or False? If false, explain why.

A - False. The sole purpose of garbage collection is to reclaim memory occupied by objects that are no longer needed, and it has no other purpose relative to necessary cleanup. An object becomes eligible for garbage collection when there are no more references to that object. However, just because an object is eligible for garbage collection doesn't mean that it will be reclaimed. The garbage collector runs in a low-priority thread, and may not run at all unless a memory shortage is detected.

Q - Before the garbage collector reclaims the memory occupied by an object, it always calls the

object's _________ method. (Provide the name of the method.) Explain why this method is one of

the methods in all new classes that you define.

A - Before the garbage collector reclaims the memory occupied by an object, it calls the object's finalizemethod. The finalize method is a member of the Object class. Since all classes inherit from the Object class, your classes also contain the default finalize method.

Q - What must you do to make effective use of the finalize method? Explain why you might want to

do this.

A - In order to make use of the finalize method, you must override it, providing the code that you want to have executed before the memory is reclaimed.

Q - You can always be confident that the finalize method will be promptly executed to perform

necessary cleanup in a Java program when an object becomes eligible for garbage collection: True

or False? If false, explain why.

A - False. Although you can be confident that the finalize method will be called before the garbage collector reclaims the memory occupied by a particular object, you cannot be certain when, or if that memory will be reclaimed. There is no guarantee that the memory will be reclaimed by the garbage collector during the execution of your program.

Q - Provide a code fragment illustrating the method call that you can make to ask the garbage

collector to run. This guarantees that garbage collection will take place: True or False? If false,

explain why.

A - False. Campione and Walrath indicate that you can ask the garbage collector to run at any time by calling the method shown below. They further point out, however, that making the request does not guarantee that your objects will be reclaimed through garbage collection.   System.gc();

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