Java – Irretrievably destroying data in Java


Is there anyway in Java to delete data (e.g., a variable value, object) and be sure it can't be recovered from memory? Does assigning null to a variable in Java delete the value from memory? Any ideas? Answers applicable to other languages are also acceptable.

Best Solution

Due to the wonders virtual memory, it is nearly impossible to delete something from memory in a completely irretrievable manner. Your best bet is to zero out the value fields; however:

  • This does not mean that an old (unzeroed) copy of the object won't be left on an unused swap page, which could persist across reboots.
  • Neither does it stop someone from attaching a debugger to your application and poking around before the object gets zeroed or crashing the VM and poking around in the heap dump.