Chapter 1
Optimizing Java Code
Many Android application developers have a good practical knowledge of the Java language from previous experience. Since its debut in 1995, Java has become a very popular programming language. While some surveys show that Java lost its luster trying to compete with other languages like Objective-C or C#, some of these same surveys rank Java as the number 1 language popularity-wise. Naturally, with mobile devices outselling personal computers and the success of the Android platform (700,000 activations per day in December 2011) Java is becoming more relevant in today's market than ever before.
Developing applications for mobile devices can be quite different from developing applications for personal computers. Today's portable devices can be quite powerful, but in terms of performance, they lag behind personal computers. For example, some benchmarks show a quad-core Intel Core i7 processor running about 20 times faster than the dual-core Nvidia Tegra 2 that is found in the Samsung Galaxy Tab 10.1.
NOTE: Benchmark results are to be taken with a grain of salt since they often measure only part of a system and do not necessarily represent a typical use-case.
This chapter shows you how to make sure your Java applications perform well on Android devices, whether they run the latest Android release or not. First, we take a look at how Android executes your code. Then, we review several techniques to optimize the implementation of a famous mathematical series, including how to take advantage of the latest APIs Android offers. Finally, we review a few techniques to improve your application's responsiveness and to use databases more efficiently.
Before you jump in, you should realize code optimization is not the first priority in your application development. Delivering a good user experience and focusing on code maintainability should be among your top priorities. In fact, code optimization should be one of your last priorities, and may not even be part of the process altogether. However, good practices can help you reach an acceptable level of performance without having you go back to your code, asking yourself “what did I do wrong?” and having to spend additional resources to fix it.