Java.lang.OutOfMemoryError: Java heap space error appearing in any application actually means there is not enough space. The JVM might have run out of memory in the heap area while trying to allocate new objects, and garbage collection couldn’t reclaim enough space. The first and foremost thing one should do is to check whether the current heap size is sufficient for the application's requirements. This can be done by reviewing the JVM parameters -Xms (initial heap size) and -Xmx (maximum heap size). If the heap size is not sufficient, then increase the heap size.

To understand a few more types of OutOfMemoryError, Its causes and solution you can refer to this blog post.

Even after increasing the heap size sometimes it doesn’t resolve the issue or if you suspect a memory leak then you have to capture a heap dump when the error occurs. In order to capture the heap dump you will have to enable these 2 parameters -XX:+HeapDumpOnOutOfMemoryError and -XX:HeapDumpPath in the JVM. The generated heap dump can then be analyzed using tools like Eclipse MAT, JVisualVM, or HeapHero to identify large objects, memory leaks, or areas where memory is being excessively retained.

Profiling your application with such tools can provide real-time insights into memory consumption patterns and object allocations. It’s also really hard to review the application code for common memory management issues like static collections not being cleared, caches without eviction policies, unclosed resources, or objects being unintentionally retained in memory.

It's always better to check if the garbage collector is running more frequently. Suppose if GC is frequent and still if the memory is not reclaimed to some sufficient extent, it's time to focus on tuning your GC settings. G1GC seems to be a more efficient collector. you can switch to this  G1GC collectorcheck this brings any visible change. There are a few options and adjusting parameters to use for G1GC. Use XX:+UseG1GC,-XX:MaxGCPauseMillis and -XX:InitiatingHeapOccupancyPercent. These can help in optimizing memory management.

Though the last suggestion, it's always better to review your third-party library usage. This is important because some libraries, without proper discarding, might have  unnecessary objects with them. If a single JVM instance can’t handle the workload even after optimizations, scaling the application horizontally by distributing the load across multiple JVM instances should be considered.