The first part is easy, there can be many answers (using various profiling tools, code inspection, analyze response time of io,database,network etc). The second part is harder: 'A memory leak in a Java program occurs when object references that are no longer needed are unnecessarily maintained.' And the third part is very hard (it puts the first 2 concepts together): Since memory leaks don't throw direct errors you need to use optimization techniques like memory profiling and/or heap debugging. Oracle has some great docs on the topic.