Why I can’t create an array with large size?

by

Theory

There are two possible exceptions:

  • OutOfMemoryError: Java heap space means your array does not fit into java heap space. In order to solve you can increase the maximum heap size by using JVM option -Xmx. Also take into account that the maximum size of object cannot be larger than the largest heap generation.
  • OutOfMemoryError: Requested array size exceeds VM limit means platform-specific size was exceeded:
    • the upper bound limit is set by the restrictions of the size type used to describe an index in the array, so theoretical array size is limited by 2^31-1=2147483647 elements.
    • the other limit is JVM/platform specific. According to chapter 10: Arrays of The Java Language Specification, Java SE 7 Edition there is no strict limit on array length, thus array size may be reduced without violating JLS.

Practice

In HotSpot JVM array size is limited by internal representation. In the GC code JVM passes around the size of an array in heap words as an int then converts back from heap words to jint this may cause an overflow. So in order to avoid crashes and unexpected behavior the maximum array length is limited by (max size – header size). Where header size depends on C/C++ compiler which was used to build the JVM you are running(gcc for linux, clang for macos), and runtime settings(like UseCompressedClassPointers). For example on my linux:

  • Java HotSpot(TM) 64-Bit Server VM 1.6.0_45 limit Integer.MAX_VALUE
  • Java HotSpot(TM) 64-Bit Server VM 1.7.0_72 limit Integer.MAX_VALUE-1
  • Java HotSpot(TM) 64-Bit Server VM 1.8.0_40 limit Integer.MAX_VALUE-2

Useful Links

More Related Contents:

  1. How do I write a correct micro-benchmark in Java?
  2. Real differences between “java -server” and “java -client”?
  3. Running jmap getting Unable to open socket file
  4. How does the JVM decided to JIT-compile a method (categorize a method as “hot”)?
  5. Class JavaLaunchHelper is implemented in both … libinstrument.dylib. One of the two will be used. Which one is undefined
  6. Analyzing gc logs
  7. Java Exceptions counter on JVM HotSpot
  8. Read Java JVM startup parameters (eg -Xmx)
  9. Encourage the JVM to GC rather than grow the heap?
  10. Does Java JIT cheat when running JDK code?
  11. What are ReservedCodeCacheSize and InitialCodeCacheSize?
  12. -XX:MaxPermSize with or without -XX:PermSize
  13. When can Hotspot allocate objects on the stack? [duplicate]
  14. What is the size of methods that JIT automatically inlines?
  15. Java using much more memory than heap size (or size correctly Docker memory limit)
  16. Where are static methods and static variables stored in Java?
  17. Does the JVM prevent tail call optimizations?
  18. Debug a java application without starting the JVM with debug arguments
  19. When is the static block of a class executed?
  20. Java user.home is being set to %userprofile% and not being resolved
  21. Find out what JVM Eclipse is running on
  22. Exception 0xC0000005 from JNI_CreateJavaVM (jvm.dll)
  23. How to hide warning “Illegal reflective access” in java 9 without JVM argument?
  24. Maximum number of parameters in Java method declaration
  25. Differences between Just in Time compilation and On Stack Replacement
  26. How do you crash a JVM?
  27. Where does the JVM store primitive variables?
  28. How to increase maximum number of JVM threads (Linux 64bit)
  29. Java seems to ignore -Xms and -Xmx options
  30. Eclipse EXCEPTION_ACCESS_VIOLATION crash

Leave a Comment