F.9. Garbage Collection

Every object uses system resources, such as memory. We need a disciplined way to give resources back to the system when they’re no longer needed; otherwise, “resource leaks” might occur that would prevent them from being reused by your program or possibly by other programs. The JVM performs automatic garbage collection to reclaim the memory occupied by objects that are no longer used. When there are no more references to an object, the object is eligible to be collected. This typically occurs when the JVM executes its garbage collector. So, memory leaks that are common in other languages like C and C++ (because memory is not automatically reclaimed in those languages) are less likely in Java, but some can still happen in subtle ways. Other types of resource leaks can occur. For example, an application may open a file on disk to modify its contents. If it does not close the file, the application must terminate before any other application can use it.