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I am trying to implement a cache-like collection of objects. The purpose is to have fast access to these objects through locality in memory since I'll likely be reading multiple objects at a time. I currently just store objects in a java collections object like vector or deque. But I do not believe this makes use of contiguous memory.
I know this can be done in C, but can it be done in Java? These objects may be of varying lengths (since they may contain strings). Is there a way to allocate contiguous memory through Java? Is there a Java collections object that would?
Please let me know.
Thanks, jbu
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In Java, all objects are dynamically allocated on Heap. This is different from C++ where objects can be allocated memory either on Stack or on Heap. In JAVA , when we allocate the object using new(), the object is allocated on Heap, otherwise on Stack if not global or static.
ArrayLists use contiguous memory. All elements in the ArrayList are located next to each other in the same memory space.
Contiguous memory allocation refers to a memory management technique in which whenever there occurs a request by a user process for the memory, one of the sections of the contiguous memory block would be given to that process, in accordance with its requirement.
Each time an array is declared in the program, contiguous memory is allocated to it.
You can't force it. If you allocate all the objects in quick succession they're likely to be contiguous - but if you're storing them in a collection, there's no guarantee that the collection will be local to the actual values. (The collection will have references to the objects, rather than containing the objects themselves.)
In addition, GC compaction will move values around in memory.
Have you actually profiled your app and found this is a bottleneck? In most cases I'd expect other optimisations could help you in a more reliable way.
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