How ‘random’ is allocation of memory when I say “new Integer” in Java?

by

What algorithms are used?

Java uses TLAB (Thread Local Allocation Buffers) for “normal” sized objects. This means each thread grab some Eden space and turns this grab of memory into individual objects. Thus small objects are typically sequential in memory for that thread, except if a new chunk of memory needs to be grabbed.

Large objects such as large arrays are allocated directly into tenured space, finding a free space which is enough for object allocated (in a single threaded manner)

Which random number generators, if any, does a JVM use for determining allocation address when allocating a memory block

It doesn’t use any random number generators for allocation. Nor would you want it to. It would be much slower and add needless complexity.

for a variable, e.g. int a;

Variables are not allocated only Objects are allocated. Variables can appear on the stack or in an objects and are usually laid out in the simplest manner possible.

when it runs the bytecode corresponding to ‘new int()’?

You can’t do new int()

BTW: There is a common misconception that if you print a new Object() and get something like Object@b7f86352 that the hexidecimal is an address. This is not the case. The address of the object can be used as a seed for a random number generated and stored in the header, but this number has nothing to do with the actual memory address and it doesn’t change as the object is moved around in memory.

More Related Contents:

  1. Circular References in Java
  2. What is the actual memory place for static variables?
  3. Size of Huge Objects directly allocated to Old Generation
  4. How to calculate HashMap memory usage in Java?
  5. Is the garbage collector guaranteed to run before Out of Memory Error?
  6. Java Memory explained (SUN JVM)
  7. What are the -Xms and -Xmx parameters when starting JVM?
  8. Java using much more memory than heap size (or size correctly Docker memory limit)
  9. Memory address of variables in Java
  10. Calculate size of Object in Java [duplicate]
  11. Java heap terminology: young, old and permanent generations?
  12. How to set the maximum memory usage for JVM?
  13. Shared Memory between two JVMs
  14. General strategy to resolve Java memory leak?
  15. How to monitor Java memory usage?
  16. java.lang.OutOfMemoryError: PermGen space [closed]
  17. Does variable = null set it for garbage collection
  18. kubernetes pod memory – java gc logs
  19. Java Refuses to Start – Could not reserve enough space for object heap
  20. Why does the (Oracle) JVM have a fixed upper limit for memory usage (-Xmx)?
  21. Can the JVM max heap size be dynamic?
  22. JVM sending back memory to OS [duplicate]
  23. Why does the JVM require warmup?
  24. Garbage collection on intern’d strings, String Pool, and perm-space
  25. Where does the JVM store primitive variables?
  26. Java BigDecimal memory usage?
  27. How JVM stack, heap and threads are mapped to physical memory or operation system
  28. How to read a verbose:GC output?
  29. Measuring time spent on GC
  30. Trick behind JVM’s compressed Oops

Leave a Comment