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Know your worst friend, the garbage collector: it can make or break performance.

Article Excerpt
All Java programmers are aware of a peculiar entity living in their Java Virtual Machine known as the Garbage Collector. Although we all use it every day, only a few of use know exactly what it is and how it works. Unquestionably useful, the Garbage Collector can hurt the performance of your application without you even knowing it. In this article you will learn about its inner workings and understand how to tame it to boost your programs.

The Garbage Collector, which I will call GC from now on, is a benevolent sentinel present in every JVM. Its role is to identify and free chunks of memory left unused by the currently running application. Its job should shed some light on the origin of the name "garbage collector." Despite the depreciating name, the GC is like Dilbert's garbage man who is very smart, even smarter than you sometimes.

During its lifecycle, an application creates a certain number of objects, that is to say a certain amount of data that consumes memory and lasts according to its role in the inner workings of the application. Let's take the simple example of a Web browser. The object corresponding to the window you look at has exactly the same life span as the application itself, while the object standing for the Google logo on the google. corn front page lasts only as long as you're on the page. As. a matter of fact, an application spawns a large amount of shortlived objects during its life span. So you can understand that defining and controlling the lifecycle of every single object generated by an application demands a tremendous amount of work from developers.

A simple example should give you a better idea of the incredible number of objects that are born and then killed. When you open a plain text file in a text editor, in our case Jext, 342,997 objects are created and destroyed. Even the simple conversion of a pound to kilograms entails the birth and the death of more than 171,000 objects in Numerical Chameleon. Imagine if the programmer had to know exactly how to handle every single object during an application's lifecycle. Yet, the slightest error can prove disastrous; this is how infamous...

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