How to explicitly perform garbage collection

Question

With its built-in garbage collection, Java allows developers to create new objects without worrying explicitly about memory allocation and deallocation, because the garbage collector automatically reclaims memory for reuse.

AFAIK Garbage Collector usually runs when your app runs out of memory. it holds a graph that represents the links between the objects and isolated objects can be freed.

Though we have System.gc(), but if you write System.gc() in your code the Java VM may or may not decide at runtime to do a garbage collection at that pointas explained by this post System.gc() in Java

So I was having some doubts regarding the Garbage collection process of java.

• I wonder if there is such method in java like free() as such in C language, that we could invoke when we explicitly want to free the part of memory allocated by a new operator.

• Also does new performs the same operation as do malloc() or calloc()?

• Are there any alternates for delete(), free(), malloc(), calloc() and sizeof() methods in java.

Answer 1

No, there aren't. Java is not c, and you're not supposed to manage memory explicitly.

Answer 2

AFAIK Garbage Collector usually runs when your app runs out of memory.

Little disagree on that. No. It runs asynchronously and collects the referenced memory locations.

I wonder if there is such method in java like free() as such in C language, that we could invoke when we explicitly want to free the part of memory allocated by a new operator.

Again System.gc() is your call then, but not 100% sure of memory clear immediately.

Also does new performs the same operation as do malloc() or calloc()?

If you mean allocation memory, then yes for that Object

Are there any alternates for delete(), free(), malloc(), calloc() and sizeof() methods in java.

AFAIK there is no direct functions to do so.

On top of my head, you need not to worry about such things and Modern JVM's are smart enoguh to handle these things.

An interesting thread here found on SO, to when GC decides to run. Hope that helps.