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JavaFX Script Language

As we already mentioned, JavaFX Script is a declarative scripting language with object-oriented support. If you are already acquainted with other languages such as Java, JavaScript, Groovy, Adobe ActionScript, or JRuby, JavaFX Script will look familiar, but there are significant differences. While supporting traditional pure scripting, it also supports the encapsulation and reuse capabilities afforded by object orientation. This allows the developer to use JavaFX to produce and maintain small- to large-scale applications. Another key feature is that JavaFX Script seamlessly integrates with Java.

Conceptually, JavaFX Script is broken down into two main levels, script and class. At the script level, variables and functions may be defined. These may be shared with other classes defined within the script, or if they have wider access rights, they may be shared with other scripts and classes. In addition, expressions called loose expressions may be created. These are all expressions declared outside of a class definition. When the script is evaluated, all loose expressions are evaluated.

A very simple script to display Hello World to the console is

println("Hello World");

Another example, showing how to do a factorial of 3, is shown in Listing 3.1.

Listing 3.1. Factorial of 3

def START = 3;
var result = START;
var a = result - 1;
while(a > 0) {
    result *= a;
    a--;
}
println("result = {result}");

Apart from the script level, a class defines instance variables and functions and must first be instantiated into an object before being used. Class functions or variables may access script level functions or variables within the same script file, or from other script files if the appropriate access rights are assigned. On the other hand, script level functions can only access class variables and functions if the class is created into an object and then only if the class provides the appropriate access rights. Access rights are defined in more detail later in this chapter.

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