In my current project (OpenGL Voxel Engine) I have a serious issue when generating models. I have a very object oriented structure, meaning that even single parameters of my vertices are Object
s. This way I am creating about 75000 Object
s for 750 voxels in about 5 seconds. Is Java really this slow when allocating new Object
s or do I miss a big failure somewhere in my code?
Is Java slow when creating Objects?
10.5k views Asked by th3falc0n AtThere are 6 answers
Objects will be slower than primitives, and they will also consume considerably more memory - so it's possible you are going overboard on them. It's hard to say without seeing more details.
75000 objects will not take a long time to create though, try this:
List<Integer> numbers = new ArrayList<Integer>();
for(int i = 0;i<75000;i++){
numbers.add(i); // Note this will autobox creating an Integer object after the first 128
}
System.out.println(numbers.size());
}
http://www.tryjava8.com/app/snippets/52d070b1e4b004716da5cb4f
Total time taken less than a second.
When I put the number up to 7,500,000 it finally took a second...
The new operator in java is very fast compared to the common approach in languages without automatic memory management (e.g. the new operator is usually faster than the malloc-command in C because it does not need a system call).
Although the new operator can still be a bottleneck, it is certainly not the problem in your case. Creating 75K objects should be WAY faster than 5 seconds.
Of course it isn't. The following code allocates 10 million objects and stores them in an array. On my 5 year old notebook, it completes in 1.4 seconds.
public class Test {
public static void main(String[] args) {
Object[] o = new Object[10_000_000];
long start = System.nanoTime();
for (int i = 0; i < o.length; i++) {
o[i] = new Object();
}
long end = System.nanoTime();
System.out.println(Arrays.hashCode(o));
System.out.println(new BigDecimal(end - start).movePointLeft(9));
}
}
... and that's even though this benchmark is quite naive in that it doesn't trigger just in time compilation of the code under test before starting the timer.
I have the same issue with creating new objects.
My object in constructor allocate single three dimensional array 64x64x64 and no more. FPS fell down to quarter of a value.
I solve this issue with reusing old object and reset it's state (BTW this method reallocate this array without lost performance).
If I move allocation array into separate method and call it after creating the object, speed does not increase to acceptable value.
This object I created is in Main game loop.
Very big question. Generally speaking, it depends from the object class definition and by the amount of work required to construct object.
Some issue:
these issues solved my problem.
See also http://oreilly.com/catalog/javapt/chapter/ch04.html
Finally let me suggest you the (deprecated) Object Pool pattern or reuse objects.
Concluding, no, generally speaking, java object creation is not slow