Java Certification: SCJP 6- Sun Certified Java Programmer Exam

Garbage Collection

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Q2. 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).

Correct Answer: A


A is correct. Garbage collection cannot be forced.
B and D are not correct as calling System.gc() or Runtime.gc() is not 100 percent
reliable, since the garbage collection thread might defer to a thread of higher 
C is incorrect as gc method does not take argument.
E makes object to be garbage collected while next time it refers.

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