VisitorLambda simplification

Author: mtumilowicz

src/main/java/visitor/VisitorLambda.java

@@ -11,29 +11,17 @@ public class VisitorLambda {
  public static class LambdaVisitor<A> implements Function<Object, A> {
  private Map<Class<?>, Function<Object, A>> fMap = new HashMap<>();
 
- public <B> Acceptor<A, B> on(Class<B> clazz) {
- return new Acceptor<>(this, clazz);
+ @SuppressWarnings(value = "unchecked")
+ public <B> LambdaVisitor<A> addHandler(Class<B> clazz, Function<B, A> handler) {
+ fMap.put(clazz, (Function<Object, A>) handler);
+ return this;
  }
 
  @Override
  public A apply( Object o ) {
  return fMap.get(o.getClass()).apply( o );
  }
 
- static class Acceptor<A, B> {
- private final LambdaVisitor visitor;
- private final Class<B> clazz;
-
- public Acceptor( LambdaVisitor<A> visitor, Class<B> clazz ) {
- this.visitor = visitor;
- this.clazz = clazz;
- }
-
- public LambdaVisitor<A> then(Function<B, A> f) {
- visitor.fMap.put( clazz, f );
- return visitor;
- }
- }
  }
 
  public static class Square {
@@ -63,22 +51,22 @@ public Rectangle( double weidht, double height ) {
  }
 
  static Function<Object, Double> areaVisitor = new LambdaVisitor<Double>()
- .on(Square.class).then( s -> s.side * s.side )
- .on(Circle.class).then( c -> Math.PI * c.radius * c.radius )
- .on(Rectangle.class).then( r -> r.height * r.weidht );
+ .addHandler(Square.class, (Square s) -> s.side * s.side )
+ .addHandler(Circle.class, c -> Math.PI * c.radius * c.radius )
+ .addHandler(Rectangle.class, r -> r.height * r.weidht );
 
  static Function<Object, Double> perimeterVisitor = new LambdaVisitor<Double>()
- .on(Square.class).then( s -> 4 * s.side )
- .on(Circle.class).then( c -> 2 * Math.PI * c.radius )
- .on(Rectangle.class).then( r -> 2 * r.height + 2 * r.weidht );
+ .addHandler(Square.class, s -> 4 * s.side )
+ .addHandler(Circle.class, c -> 2 * Math.PI * c.radius )
+ .addHandler(Rectangle.class, r -> 2 * r.height + 2 * r.weidht );
 
  public static void main( String[] args ) {
  List<Object> figures = Arrays.asList( new Circle( 4 ), new Square( 5 ), new Rectangle( 6, 7 ) );
 
- double totalArea = figures.stream().map( areaVisitor ).reduce( 0.0, (v1, v2) -> v1 + v2 );
+ double totalArea = figures.stream().map( areaVisitor ).reduce( 0.0, Double::sum);
  System.out.println("Total area = " + totalArea);
 
- double totalPerimeter = figures.stream().map( perimeterVisitor ).reduce( 0.0, (v1, v2) -> v1 + v2 );
+ double totalPerimeter = figures.stream().map( perimeterVisitor ).reduce( 0.0, Double::sum);
  System.out.println("Total perimeter = " + totalPerimeter);
  }
 }