Java objects as functions parameters and returns

Java objects must be instantiated and referenced by a program variable. The object reference is stored in the variable and can be passed as a parameter, or returned from a function.

The Java objects are passed by reference to functions. This means that the called function does not get a clone of the object, but rather a handle to the original object. The function can then manipulate and modify the original object provided by the caller:

IMPORT JAVA java.lang.StringBuffer

MAIN
  DEFINE x java.lang.StringBuffer
  LET x = StringBuffer.create()
  CALL change(x)
  DISPLAY x.toString()
END MAIN

FUNCTION change(sb java.lang.StringBuffer)
  CALL sb.append("abc")
END FUNCTION

Similarly, Java object references can be returned from functions. Use the RETURNS clause in the function definition, to specify the type of Java object returned by the function:

IMPORT JAVA java.lang.StringBuffer

MAIN
  DEFINE x java.lang.StringBuffer
  LET x = build()
  DISPLAY x.toString()
END MAIN

FUNCTION build() RETURNS java.lang.StringBuffer
  DEFINE sb java.lang.StringBuffer
  LET sb = StringBuffer.create()   -- Creates a new object.
  CALL sb.append("abc")
  RETURN sb  -- Returns the reference to the object, not a copy/clone.
END FUNCTION