Question

This thread, and this page:

It [OutOfMemoryError] will never be thrown unless the JVM tries a full garbage collection
first, including removal of softly/weakly referenced objects.

As for this piece of code,

//.. allocate reserved memory
try {
    //.. calculation which requires alot of memory even after optimized
} catch (java.lang.OutOfMemoryError e){
    System.gc(); 
    //.. hedge recovery
}

Is the call to System.gc() redundant?

Is it already guaranteed that JVMs (according to JVMS) had run the GC before throwing java.lang.OutOfMemoryError?

Answer 1

From here:

Thrown when the Java Virtual Machine cannot allocate an object because it is out of memory, and no more memory could be made available by the garbage collector.

So, OutOfMemoryException is thrown after GC cannot free more memory.