OutOfMemoryError exception is usually thrown whenever the Java VIRTUAL Machine runs out of memory and cannot allocate an object. The trash collector was unable to release any more memory. OutOfMemoryError frequently indicates that you're doing something incorrectly, such as holding on to objects for too long or processing too much data at once. It can also suggest an out-of-control issue, as in a third-party library that caches strings or perhaps an application server that doesn't clear up after deployments. And it doesn't always have anything to do with the items on the HEAP. When a native allocation cannot be satisfied, the java.lang.OutOfMemoryError exception can be thrown by native library code (for example, if swap space is low). Let's look at some of the scenarios in which the OutOfMemory issue can occur.

• Java heap space: This problem is caused by applications that utilise too many finalizers. If a class does have a finish method, trash collection does not reclaim space for objects of that kind. INSTEAD, the objects get queued for finalisation, which happens later after garbage collection.
• GC Overhead limit surpassed: This ERROR means that the garbage collector is constantly operating and that the Java application is progressing very slowly. A java.lang.OutOfMemoryError is thrown after a garbage collection if the Java process spends more than approximately 98 per cent of its time doing garbage collection and recovers less than 2% of the heap and has done so far the last 5 (compile-time constant) subsequent garbage collections.
• Metaspace: Metadata for Java classes is stored in native memory. Assume that the metaspace for class metadata has been depleted, as in java.lang. The exception OutOfMemoryError with a detail MetaSpace is thrown. A java.lang.OutOfMemory Exception is thrown when the amount of native memory required for class metadata surpasses MaxMetaSpaceSize. The exception OutOfMemoryError with a detail MetaSpace is thrown.
• Requested array SIZE exceeds VM limit: This phrase implies that the application tried to allocate an array that was larger than the heap capacity.
• Permgen space is thrown: The PermGen space error means that the memory space allocated to the Permanent Generation has been used up.
• Out of swap space: This apparent exception happens when a native heap allocation fails and the native heap is nearing exhaustion. Operating-system-level faults are frequently the cause of the java.lang.OutOfMemoryError: Out of Swap Space error.
• reason stack_trace_with_native_method: When this error message (reason stack trace with the native method) is thrown, a stack trace with a native method as the top frame is printed. This indicates that a native method has experienced an allocation failure.