/**
 * Java and Object Closures.
 * Although Java does not have closure, you can get something very similar
 * using interfaces and creation of classes that implement interface within
 * a function. For instance, how is the below much different from a the
 * incrementer closure in Go from homework 3??
 * 
 * @author gtowell
 * Created: Nov 20, 2022   gtowell
 */
public class ObjClo {

    /**
     * the interface that the ObjectClosure will implement.
     * Usually this would be a common, well-defined interface
     * but for this purpose a private one-off will do.
     */
    private interface Funcer {
        int doFunc(int val);
    }

    /**
     * A function that returns an object closure.
     * @param val
     * @return an instance of a class that implements Funcer
     */
    public Funcer makeIncrementer(final int val) {
        // define a new class!! within this function.
        final class IFuncer implements Funcer {
            private int jj = 0; // count the number of calls

            /**
             * The incrementer "closure"
             */
            public int doFunc(int vv) {
                return (jj++) * val;
            }
        }
        //val=val+10; // This causes the compiler to barf!!
        return new IFuncer(); 
    }
    
    public static void main(String[] args) {
        (new ObjClo()).doo();
    }

    /**
     * Example!
     */
    public void doo() {
        Funcer ff = makeIncrementer(7);
        System.out.println(ff.doFunc(0));
        System.out.println(ff.doFunc(0));
        System.out.println(ff.doFunc(0));
        System.out.println(ff.doFunc(0));
    }
}