Question

Java programmers know that JVM runs a Garbage Collector, and System.gc() would just be a suggestion to JVM to run a Garbage Collector. It is not necessarily that if we use System.gc(), it would immediately run the GC.

Please correct me if I misunderstand Java’s Garbage Collector.

Is/are there any other way/s doing memory management other than relying on Java’s Garbage Collector?
If you intend to answer the question by some sort of programming practice that would help managing the memory, please do so.

Answer 1

The most important thing to remember about Java memory management is "nullify" your reference.

Only objects that are not referenced are to be garbage collected.

For example, objects in the following code is never get collected and your memory will be full just to do nothing.

List objs = new ArrayList();
for (int i = 0; i  < Integer.MAX_VALUE; i++) objs.add(new Object());

But if you don’t reference those object … you can loop as much as you like without memory problem.

List objs = new ArrayList();
for (int i = 0; i  < Integer.MAX_VALUE; i++) new Object();

So what ever you do, make sure you remove reference to object to no longer used (set reference to null or clear collection).

When the garbage collector will run is best left to JVM to decide. Well unless your program is about to start doing things that use a lot of memory and is speed critical so you may suggest JVM to run GC before going in as you may likely get the garbaged collected and extra memory to go on. Other wise, I personally see no reason to run System.gc().

Hope this helps.