| Topic |
Notes |
| JVM's garbage collection. |
- Java manages memory for you.
- The JVM will only perform garbage collection if it needs more memory to continue
executing. Helps efficiency.
- You can make a call to garbage collection with System.gc(), but this does not guarantee
when it will happen.
- JVM runs the object's finalize() method prior to garbage collection. In other
words, Java notifies the object.
- The garbage collector does not claim objects in any certain order. Helps
efficiency.
- If the JVM is halted at the conclusion of the program, it could be that no garbage
collection ever occurs.
|
| Candidate for Garbage Collection |
- Any object is a candidate for garbage collection when your program can no longer
reference it (orphaned object).
- Local variables are candidate for garbage collection when the method returns (finished).
- Any object is available for garbage collection after it is set to
"null". (ex: strX="Hello"; strX=null;)
- If you reuse a reference object, the prior object is a candidate. (ex: String strX
="Hello"; strX = "Hello2") or (ex: int [] MyArray =
{1,2,3}; MyArray = new int[3];)
|
| Other notes |
- finalize() could be a good place to close files and other resources.
- Always invoke the superclass's finalize() method if you override finalize().
- gc() (in Runtime & System) will allow you to directly run the garbage collector.
- finalize() signature:
protected void finalize() throws Throwable()
- To use finalize() you must use a try-catch block or rethrow the error
object.
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