28.4.2 Declaring Java classes

The <declare-class-clause> clause denotes importation of Java classes.

<declare-class-clause> → (class <typed-ident> <slot>* <string>) 
<slot> → <field> | <method> | <constructor>
<field> → (field <modifier> <typed-ident> <string>)
<method> → (method <modifier> <typed-ident> (<typed-ident>*) <string>)
<constructor> → (constructor <ident> (<typed-ident>*))
<modifier> → public | private | protected
     | static | final | synchronized | abstract

When the compiler encounters a Java class declaration, it automatically creates a predicate. If the class identifier is id, the predicate is named id?. In addition, the compiler generates functions that fetch and set the field values. For a field named f, these functions are named id-f and id-f-set!. Methods and constructors are also always prefixed the name of the class. That is, for a method named m of a class k, the Scheme name of the method is k-m.

Example:

(module java-example
   (java (class point
            (constructor new-default ())
            (field x::int "x")
            (method show::void (::point) "show")
            (method static statistics::int () "PointStatistics")
            "Point")
         (class point-3d::point
            "Point3D")))

(let ((p (point-new-default)))
   (print (point? p))   -| #t
   (point-x-set! p 3)
   (print (point-x p))) -| 3

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