Understanding the Java Virtual Machine: Memory Management
by Kevin Jones
This course covers all aspects of garbage collection in Java, including how memory is split into generations and managed and how the different collectors do their job. We also cover the classes you can use to interact with the garbage collection, such as Soft, Weak, and PhantomReference.
What you'll learn
Garbage Collection (GC) is a fundamental part of Java. Understanding how GC works is core to understanding how the Java Virtual Machine (JVM) works and will help you write better applications and to improve the performance of those applications. This course will look at all aspects of garbage collection, including looking at what 'young' and 'old' generations are, how the JVM moves objects between eden and survivor spaces, how memory is promoted into the 'old' generation, how different garbage collectors work, and how they affect the running of your application. We will also look at 'card tables' and how they help manage memory in the old generation. We will examine each of the garbage collectors including the serial and parallel collectors; the CMS collector and the G1 collector. We cover the tools you can use to monitor GC including jstat and VisualVM. Finally we look at ways you interact with the GC through classes Such as Soft, Weak, and PhantomReference and their associated helpers ReferenceQueue and WeakHashMap.
About the author
A long time ago in a university far, far away Kevin fell in love with programming. Initially on the university's DEC20 computer doing BASIC and Pascal and a little bit of Fortran. His first job had him writing batch PL/1 on an IBM mainframe where he also discovered the arcane delights of JCL. He soon realized the multiuser systems were not for him after discovering the delights of dBase IV on IBM PCs. From here it was all downhill as he became addicted to C and the Windows API. Just missing out ... moreon coding for Windows 1, he did code for the other 16 bit versions of Windows, 2 and 3, including the various network-ready versions. He still remembers the awkwardness of having to carry an IBM Token Ring MAU with him wherever he went.
After trying to pretend that Windows and C were really object oriented he decided that it would be better to learn C++. It was around this point that he realized that as well as writing code for a living he could be paid for telling people how to write code for a living. He taught Windows, MFC and C++ for a UK training company before his spirit was broken on the back of the OLE support in MFC when he finally stepped away from the nightmare of unmanaged code to the nirvana of the managed runtime called Java.
It was at this time that he spoke at several JavaOne conferences usually on the subject of Servlets, JavaServer Pages and tag libraries. After buying the Sun employees copious amounts of Apple Martini Kevin was invited onto the expert groups for the Servlet and JSP specifications.
Oh, how he laughed when .Net appeared and the same arguments raged about non-deterministic destruction and garbage collection that were now so old hat in the Java world. He finally got his hands dirty in C# and .Net about eight years ago, again working in the web tier and hating every minute of the using the monstrosity that was and is ASP.Net Web Forms. It wasn't until MVC appeared that he finally felt he had come home to Microsoft.
Now of course MVC is so last year and Kevin is focusing more and more on rich clients using JavaScript and tools such as Knockout and AngularJS. He believes that JavaScript is the best thing since, well, JavaScript.
He still retains his passion for developing and teaching; spending about a quarter of the year doing the latter and most of the time doing the former.
When not stuck in front of a computer you can find him: with his nose in a book, a good one preferably, but almost any book would do; watching a film; walking; running; or annoying his wife by watching sports on television.