Introduction to scripting in Java, Part 2

Find out what else you need to know about scripting in this second half of the JavaWorld excerpt from Dejan Bosanac's Scripting in Java: Languages, Frameworks, and Patterns (Addison Wesley Professional, August 2007)

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A Comparison of Scripting and System Programming

Every decision made during the language design process is directly related to the programming style used in that language and its usability in the development process.

In this section, I do not intend to imply one style is better than the other. Instead, my objective is to summarize the strengths and weaknesses of both approaches so that we can proceed to Chapter 2, where I discuss how best to incorporate them into the development process.

Runtime Performance

It is clear programs written in system-programming languages have better runtime performance than equivalent scripts in most cases, for a few reasons:

The fact that the script could be compiled to intermediate bytecode makes these interpreter performance penalties more acceptable. But the machine code is definitely more optimized than the intermediate code.

We have to take another point of view when talking about runtime performance, however. Many people approach runtime performance by asking which solution is faster. The more important question, which is often neglected, is whether a particular solution is fast enough.

You must take into consideration the trade-offs between the benefits and the runtime performance that each approach provides when you are thinking about applying a certain technology in your project. If the solution brings quality to your development process and still is fast enough, you should consider using it.

A recent development trend supports this point of view. Many experts state you should not analyze performance without comparing it to measurements and goals. This leads to debate concerning whether to perform premature or prudent optimization. The latter approach assumes you have a flexible system, and only after you've conducted the performance tests and found the system bottlenecks should you optimize those parts of your code.

Deciding whether scripting is suitable for some tasks in your development process must be driven by the same question. For instance, say you need to load a large amount of data from a file, and developing a system-programming solution to accomplish the task would take twice as long as developing a scripting approach. If both the system-programming and scripting solutions needed 1 second to load the data and the interpreter required an additional 0.1 second to compile the script to the bytecode, you should consider scripting to be a fast enough solution for this task. As we will see in a moment, scripts are much faster to write (because of the higher level of abstraction they introduce), and the end users of your project probably wouldn't even notice the performance advantage of the system-programming solution that took twice as much time to develop.

If we take another point of view, we can conclude the startup cost of executing programs written in dynamic languages could be close to their compiled alternatives. The first important thing to note is the fact that bytecode is usually smaller than its equivalent machine code. Experts who support this point of view stress that processors have increased in speed much faster than disks have. This leads to the thinking that the in-memory operations of the just-in-time compilers (compiling the bytecode to the machine code) are not much more expensive than the operation of loading the large sequence of machine code from the disk into memory.

To summarize, it is clear system-programming languages are faster than scripting languages. But if you don't need to be restricted by only one programming language, you should ask yourself another question: What is the best tool for this task? If the development speed is more important and the runtime performance of the scripting solution is acceptable, there is your answer.

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