import org.junit.Test;

public class VisitorTest {
    abstract class Parent {
        public abstract void accept(Visitor visitor);
    }

    class Tree extends Parent {
        public void accept(Visitor visitor) {
            visitor.visit(this);
        }
    }

    class Home extends Parent {
        public void accept(Visitor visitor) {
            visitor.visit(this);
        }
    }

    interface Visitor {
        void visit(Home value);
        void visit(Tree value);
    }

    class CountVisitor implements Visitor {
        int homeCount;
        int treeCount;

        @Override
        public void visit(Home value) {
            homeCount++;
        }

        @Override
        public void visit(Tree value) {
            treeCount++;
        }

        public int getHomeCount() {
            return homeCount;
        }

        public int getTreeCount() {
            return treeCount;
        }

    }

    @Test
    public void testVisitor() {
        CountVisitor visitor = new CountVisitor();
        Parent[] values = {new Tree(), new Home(), new Tree()};
        for (Parent value : values) {
            value.accept(visitor);
        }
        System.out.println("homes: " + visitor.getHomeCount() + ", trees: "
                        + visitor.getTreeCount());
    }

}