Passing variable arguments (varargs)

Java supports variable arguments in method definitions with the ellipsis notation, allowing callers to pass a different number of arguments depending on the need. A typical example is a message print method:

import java.lang.String;

public class MyClass {
    public static void ShowStrings( String... sl ) {
        for ( String s : sl )
            System.out.println(s);
    }
}

In order to call such a method from the Genero program, create a Java array of the type of the variable argument, fill the array with objects and call the method with that array:

IMPORT JAVA java.lang.String
IMPORT JAVA MyClass

MAIN
    TYPE sl_t ARRAY[] OF java.lang.String
    DEFINE sl ARRAY[] OF java.lang.String
    LET sl = sl_t.create(2)
    LET sl[1] = "Value 1"
    LET sl[2] = "Value 2"
    CALL MyClass.ShowStrings(sl)
END MAIN

If the Java class cannot be modified, consider implementing a function to wrap calls to the Java method, with a varying number of arguments. It can for example take a BDL dynamic array as parameter, to simplify the callers code:

IMPORT JAVA java.lang.String
IMPORT JAVA MyClass

MAIN
    DEFINE a DYNAMIC ARRAY OF STRING
    LET a[1] = "Value 1"
    LET a[2] = "Value 2"
    LET a[3] = "Value 3"
    CALL my_show_strings(a)
    LET a[4] = "Value 1"
    LET a[5] = "Value 2"
    CALL my_show_strings(a)
END MAIN

FUNCTION my_show_strings(sa)
    TYPE sl_t ARRAY[] OF java.lang.String
    DEFINE sa DYNAMIC ARRAY OF STRING
    DEFINE sl ARRAY[] OF java.lang.String
    DEFINE i INTEGER
    LET sl = sl_t.create(sa.getLength())
    FOR i=1 TO sa.getLength()
        LET sl[i] = sa[i]
    END FOR
    CALL MyClass.ShowStrings(sl)
END FUNCTION

If the Java class can be modified, a good practice is to write overloaded methods, using a static number of arguments:

public class MyClass {
    private static void _ShowStrings( String... sl ) {
        for ( String s : sl )
            System.out.println(s);
    }
    public static void ShowStrings(String s1) {
        _ShowStrings(s1);
    }
    public static void ShowStrings(String s1, String s2) {
        _ShowStrings(s1, s2);
    }
    public static void ShowStrings(String s1, String s2, String s3) {
        _ShowStrings(s1, s2, s3);
    }
}