Interview question: How are objects in Java stored in memory?
All objects in Java are dynamically allocated on the heap.
The heap in Java is created when the JVM (Java Virtual Machine) starts up. The heap may dynamically increase or decrease in size at application runtime. When a variable of a class type is declared a reference is created (but no heap memory is allocated yet). Only when a variable is initialized using the “new” keyword is memory allocated on the heap. As the application runs, periodically, the Java garbage collector will remove unneeded object allocations from the heap.
New Java developers often instantiate many more objects than are needed. It is important to remember whenever the “new” keyword is used, it consumes heap memory and ultimately impacts the performance of the application. It is for this reason, utilizing the Singleton pattern, or caching frequently used or invariant objects can greatly improve the performance of an application.