Showing how to access a kotlin "public final" class members from Java (Java interop)

CallingVarInClass.java

/**
 * 6/24/2020
 * A java class accessing {@code var} and its variants defined in a kotlin {@code public final} class.
 *
 * @author srdpatel
 * @since 1.0
 */
public class CallingVarInClass {

    public static void main(String[] args) {
        accessVar();
    }

    /**
     * 6/23/2020
     * <p>
     * Accessing kotlin members.
     * </p>
     *
     * @author srdpatel
     * @since 1.0
     */
    public static void accessVar() {

        /*
         * 6/23/2020
         * "VarInClass" is a kotlin "public final" class.
         * We will access few members of that class by creating an object of the class.
         *
         * @since 1.0
         */
        VarInClass varInClass = new VarInClass();

        /*
         * 6/24/2020
         * "varInClassCompileTime" is defined in the "public final" kotlin class as:
         * ```
         * var varInClassCompileTime = "var in class for known value at compile time"
         * ```
         * The kotlin compiler makes such a variable "private" and generates two
         * additional "public" getter-setter methods.
         * We are accessing the kotlin "var" variable through such a "public" getter
         * method.
         *
         * @since 1.0
         */
        String varInClassCompileTime = varInClass.getVarInClassCompileTime();

        //prints: var in class for known value at compile time
        System.out.println(varInClassCompileTime);

        /*
         * 6/24/2020
         * We are reassigning the kotlin "var" variable through a "public" setter
         * method generated by the kotlin compiler for the "var" variable defined
         * in a kotlin "public final" class as:
         * ```
         * var varInClassCompileTime = "var in class for known value at compile time"
         * ```
         *
         * @since 1.0
         */
        varInClass.setVarInClassCompileTime("from java setter: var in class: compile time");

        //prints: from java setter: var in class: compile time
        System.out.println(varInClass.getVarInClassCompileTime());

        /*
         * 6/24/2020
         * We are accessing the kotlin "var" variable through a "public" getter
         * method generated by the kotlin compiler for the "var" variable defined
         * in a kotlin "public final" class as:
         * ```
         * var varInClassRunTime = someFun()
         * ```
         *
         * @since 1.0
         */
        String varInClassRunTime = varInClass.getVarInClassRunTime();

        //prints: runtime value from the function
        System.out.println(varInClassRunTime);

        /*
         * 6/24/2020
         * We are reassigning the kotlin "var" variable through a "public" setter
         * method generated by the kotlin compiler for the "var" variable defined
         * in a kotlin "public final" class as:
         * ```
         * var varInClassRunTime = someFun()
         * ```
         *
         * @since 1.0
         */
        varInClass.setVarInClassRunTime("from java setter: var in class: run time");

        //prints: from java setter: var in class: run time
        System.out.println(varInClass.getVarInClassRunTime());

        /*
         * 6/24/2020
         * We are accessing the kotlin "public var" variable defined in a kotlin "public final" class as:
         * ```
         * @JvmField
         * var jvmFieldVarInClass = someFun()
         * ```
         *
         * @since 1.0
         */
        varInClass.jvmFieldVarInClass = "new value from java";

        //prints: new value from java
        System.out.println(varInClass.jvmFieldVarInClass);

        /*println(varInClass.varInClassPrivate);*/ //we cannot access "private" members

        /*
         * 6/24/2020
         * We are accessing the kotlin "public" function defined in a kotlin "public final" class as:
         * ```
         * fun publicFun() = "public fun"
         * ```
         *
         * @since 1.0
         */
        varInClass.publicFun();

        /*println(varInClass.someFun());*/ //We cannot access "private" functions.
    }
}