Java Quick Reference - Garbage Collection

Language Fundamentals

Operators and Assignments

Flow Control and Exceptions

Declarations and Access Control

Garbage Collection

Overloading and Overriding

Threads

The java.lang Package

The java.util Package

The java.awt Package

The java.io Package

References

Miscellaneous Notes

Tips & Traps

Mock Exams

Garbage Collection Certification - Eligibility

variables and objects are eligible for garbage collection when they become unreachable
following summarizes the normal duration of a declared object or variable

Declaration	Duration
static field	as long as the class is loaded
instance field	for the life of the instance
Array components	as long as the array is referenced
Method parameters	until method execution ends
Constructor parameters	until the constructor execution ends
Exception handling parameters	until the catch clause completes execution
Local variables	in a for-loop, until the loop completes in a code-block, until the code block completes

any variable set to null automatically becomes eligible for garbage collection

gc and the String pool

You may run across mock exam questions or discussions that state Strings created as part of the String pool are never garbage collected. This may well be true as garbage collection is implementation dependent.

The certification exam will not contain questions that rely on specific implementations of any JVM; for exam purposes it is unlikely you will see any gc questions involving pooled Strings. Just remember once an Object reference has been set to null it is eligible for garbage collection.

Behaviour

Eligibility

finalize()