How to make the java system release Soft References?

Question

I\'m going to use a SoftReference-based cache (a pretty simple thing by itself). However, I\'ve came across a problem when writing a test for it.

The objective of th

Answer 1

This piece of code forces the JVM to flush all SoftReferences. And it's very fast to do.

It's working better than the Integer.MAX_VALUE approach, since here the JVM really tries to allocate that much memory.

try {
    Object[] ignored = new Object[(int) Runtime.getRuntime().maxMemory()];
} catch (OutOfMemoryError e) {
    // Ignore
}

I now use this bit of code everywhere I need to unit test code using SoftReferences.

Update: This approach will indeed work only with less than 2G of max memory.

Also, one need to be very careful with SoftReferences. It's so easy to keep a hard reference by mistake that will negate the effect of SoftReferences.

Here is a simple test that shows it working every time on OSX. Would be interested in knowing if JVM's behavior is the same on Linux and Windows.

for (int i = 0; i < 1000; i++) {
    SoftReference