Expected usage is one instance of this class per major logical
operation, e.g. creating a connection, preparing a statement,
adding an entry to a specific cache etc.
The logical operation would call isLowMemory() before starting
the operation, and thrown a static exception if it returns true.
If during the operation an OutOfMemoryException is thrown the
operation would call setLowMemory() and throw its static exception
representing low memory.
Future enhancments could be a callback mechanism for modules where they register they can reduce memory usage on a low memory situation. These callbacks would be triggered by a call to setLowMemory. For example the page cache could reduce its current size by 10% in a low memory situation.
| Modifier and Type | Field and Description |
|---|---|
| private long | lowMemory
Free memory seen when caller indicated an out of memory situation. |
| private long | whenLowMemorySet
Time in ms corresponding to System.currentTimeMillis() when lowMemory was set. |
| Access | Constructor and Description |
|---|---|
| public |
| Modifier and Type | Method and Description |
|---|---|
| public boolean | isLowMemory()
Return true if a low memory water mark has been set and the current free memory is lower than it. |
| public void | setLowMemory()
Set a low memory watermark where the owner of this object just hit an OutOfMemoryError. |
| lowMemory | back to summary |
|---|---|
| private long lowMemory Free memory seen when caller indicated an out of memory situation. Becomes a low memory watermark for five seconds that causes isLowMemory to return true if free memory is lower than this value. This allows the JVM a chance to recover memory rather than start new operations that are probably doomed to failure due to the low memory. | |
| whenLowMemorySet | back to summary |
|---|---|
| private long whenLowMemorySet Time in ms corresponding to System.currentTimeMillis() when lowMemory was set. | |
| LowMemory | back to summary |
|---|---|
| public LowMemory() | |
| isLowMemory | back to summary |
|---|---|
| public boolean isLowMemory() Return true if a low memory water mark has been set and the current free memory is lower than it. Otherwise return false. | |
| setLowMemory | back to summary |
|---|---|
| public void setLowMemory() Set a low memory watermark where the owner of this object just hit an OutOfMemoryError. The caller is assumed it has just freed up any references it obtained during the operation, so that the freeMemory call as best as it can reflects the memory before the action that caused the OutOfMemoryError, not part way through the action.
| |