How do I predict when I'm going to run out of memory

We have a swing based application that does complex processing on data. One of the prerequisites for our software is that any given column cannot have too many unique values. If the number is numeric, the user would need to discretize the data before they could from our tool.

Unfortunately, the algorithms we are using are combinatorially expensive in memory depending on the number of unique values per column. Right now with the wrong dataset, the app would run out of memory very quickly. Before doing one of these operations that would run out of memory, we should be able to calculate roughly how much memory the operation will need. It would be nice if we could check how much memory the app currently is using, estimate if the app is going to run out of memory, and show an error message accordingly rather than running out of memory. Using java.lang.Runtime, we can find the free memory, total memory, and max memory, but is this really helpful? Even if it appears we won't have enough heap开发者_开发百科 space, it could be that if we wait 30 milliseconds the garbage collector will run, and suddenly we have more than enough heap space to run our operation. Is there anyway to really predict if we are going to run out of memory?

I have done something similar for a database application where the number of rows that were loaded could not be estimated. So in the loop that processes the result set I'm calling a "MemorWatcher" method that would check the memory that was free.

If the available memory goes under a certain threshold the watcher would force a garbage collection and re-check. If there still wasn't enough memory the watcher method signals this to the caller with an exception. The caller can gracefully recover from that exception - as opposed to the OutOfMemoryException which sometimes leaves Swing totally unstable.

I don't have expertise on this, but I feel you can take an extra step of bytecode analysis using ASM to preempt bugs like null pointer exception, out of memory exception etc.

Unless you run your application with the maximum amount of memory you need from the outset (using -Xms) I don't think you can achieve anything useful, since other applications will be able to consume memory before your app needs it.

Have you considered using Soft/WeakReferences, and letting garbage collection reap objects that you could possible recalculate/regenerate on the fly ?