There are several ways to handle such situation. The first and most straightforward way to overcome the issue is to migrate the system to an instance with more memory.
Other possibilities would involve fine-tuning the OOM killer, scaling the load horizontally across several small instances or reducing the memory requirements of the application.
One solution which we are not keen to recommend involves increasing swap space. When you recall that Java is a garbage collected language, then this solution already seems less lucrative. Modern GC algorithms are efficient when running in physical memory, but when dealing with swapped allocations the efficiency is hammered. Swapping can increase the length of GC pauses in several orders of magnitude, so you should think twice before jumping to this solution.