Below is a small test I've coded to educate myself on references API. I thought this would never throw OOME but it is throwing it. I am unable to figure out why. appreciate any help on this.
public static void main(String[] args)
{
Map<WeakReference<Long>, WeakReference<Double>> weak = new HashMap<WeakReference<Long>, WeakReference<Double>>(500000, 1.0f);
ReferenceQueue<Long> keyRefQ = new ReferenceQueue<Long>();
ReferenceQueue<Double> valueRefQ = new ReferenceQueue<Double>();
int totalClearedKeys = 0;
int totalClearedValues = 0;
for (long putCount = 0; putCount <= Long.MAX_VALUE; putCount += 100000)
{
weak(weak, keyRefQ, valueRefQ, 100000);
totalClearedKeys += poll(keyRefQ);
totalClearedValues += poll(valueRefQ);
System.out.println("Total PUTs so far = " + putCount);
System.out.println("Total KEYs CLEARED so far = " + totalClearedKeys);
System.out.println("Total VALUESs CLEARED so far = " + totalClearedValues);
}
}
public static void weak(Map<WeakReference<Long>, WeakReference<Double>> m, ReferenceQueue<Long> keyRefQ,
ReferenceQueue<Double> valueRefQ, long limit)
{
for (long i = 1; i <= limit; i++)
{
m.put(new WeakReference<Long>(new Long(i), keyRefQ), new WeakReference<Double>(new Double(i), valueRefQ));
long heapFreeSize = Runtime.getRuntime().freeMemory();
if (i % 100000 == 0)
{
System.out.println(i);
System.out.println(heapFreeSize / 131072 + "MB");
System.out.println();
}
}
}
private static int poll(ReferenceQueue<?> keyRefQ)
{
Reference<?> poll = keyRefQ.poll();
int i = 0;
while (poll != null)
{
//
poll.clear();
poll = keyRefQ.poll();
i++;
}
return i;
}
}
And below is the log when ran with 64MB of heap
Total PUTs so far = 0
Total KEYs CLEARED so far = 77982
Total VALUESs CLEARED so far = 77980
100000
24MB
Total PUTs so far = 100000
Total KEYs CLEARED so far = 134616
Total VALUESs CLEARED so far = 134614
100000
53MB
Total PUTs so far = 200000
Total KEYs CLEARED so far = 221489
Total VALUESs CLEARED so far = 221488
100000
157MB
Total PUTs so far = 300000
Total KEYs CLEARED so far = 366966
Total VALUESs CLEARED so far = 366966
100000
77MB
Total PUTs so far = 400000
Total KEYs CLEARED so far = 366968
Total VALUESs CLEARED so far = 366967
100000
129MB
Total PUTs so far = 500000
Total KEYs CLEARED so far = 533883
Total VALUESs CLEARED so far = 533881
100000
50MB
Total PUTs so far = 600000
Total KEYs CLEARED so far = 533886
Total VALUESs CLEARED so far = 533883
100000
6MB
Total PUTs so far = 700000
Total KEYs CLEARED so far = 775763
Total VALUESs CLEARED so far = 775762
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
at Referencestest.weak(Referencestest.java:38)
at Referencestest.main(Referencestest.java:21)