TrashVisitor.java

// patterns/trashvisitor/TrashVisitor.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// {java patterns.trashvisitor.TrashVisitor}
package trashvisitor;

import patterns.trash.*;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

// Specific group of algorithms packaged
// in each implementation of Visitor:
class PriceVisitor implements Visitor {
    private double alSum; // Aluminum
    private double pSum; // Paper
    private double gSum; // Glass
    private double cSum; // Cardboard

    public static void show(String s) {
        System.out.println(s);
    }

    @Override
    public void visit(Aluminum al) {
        double v = al.weight() * al.value();
        show("value of Aluminum= " + v);
        alSum += v;
    }

    @Override
    public void visit(Paper p) {
        double v = p.weight() * p.value();
        show("value of Paper= " + v);
        pSum += v;
    }

    @Override
    public void visit(Glass g) {
        double v = g.weight() * g.value();
        show("value of Glass= " + v);
        gSum += v;
    }

    @Override
    public void visit(Cardboard c) {
        double v = c.weight() * c.value();
        show("value of Cardboard = " + v);
        cSum += v;
    }

    @Override
    public void total() {
        show(
                "Total Aluminum: $" + alSum + "\n" +
                        "Total Paper: $" + pSum + "\n" +
                        "Total Glass: $" + gSum + "\n" +
                        "Total Cardboard: $" + cSum);
    }
}

class WeightVisitor implements Visitor {
    private double alSum; // Aluminum
    private double pSum; // Paper
    private double gSum; // Glass
    private double cSum; // Cardboard

    public static void show(String s) {
        System.out.println(s);
    }

    @Override
    public void visit(Aluminum al) {
        alSum += al.weight();
        show("Aluminum weight = " + al.weight());
    }

    @Override
    public void visit(Paper p) {
        pSum += p.weight();
        show("Paper weight = " + p.weight());
    }

    @Override
    public void visit(Glass g) {
        gSum += g.weight();
        show("Glass weight = " + g.weight());
    }

    @Override
    public void visit(Cardboard c) {
        cSum += c.weight();
        show("Cardboard weight = " + c.weight());
    }

    @Override
    public void total() {
        show("Total weight Aluminum:" + alSum);
        show("Total weight Paper:" + pSum);
        show("Total weight Glass:" + gSum);
        show("Total weight Cardboard:" + cSum);
    }
}

public class TrashVisitor {
    public static void main(String[] args) {
        List<Trash> bin = new ArrayList<>();
        // ParseTrash still works, without changes:
        ParseTrash.fillBin("trashvisitor", bin);
        List<Visitor> visitors = Arrays.asList(
                new PriceVisitor(), new WeightVisitor());
        bin.forEach(t -> {
            Visitable v = (Visitable) t;
            visitors.forEach(visitor -> v.accept(visitor));
        });
        visitors.forEach(Visitor::total);
    }
}
/* Output: (First and Last 10 Lines)
Loading patterns.trashvisitor.Glass
Loading patterns.trashvisitor.Paper
Loading patterns.trashvisitor.Aluminum
Loading patterns.trashvisitor.Cardboard
value of Glass= 12.420000225305557
Glass weight = 54.0
value of Paper= 2.2000000327825546
Paper weight = 22.0
value of Paper= 1.1000000163912773
Paper weight = 11.0
...________...________...________...________...
value of Cardboard = 5.060000091791153
Cardboard weight = 22.0
Total Aluminum: $860.0499778985977
Total Paper: $35.80000053346157
Total Glass: $150.1900027245283
Total Cardboard: $40.02000072598457
Total weight Aluminum:515.0
Total weight Paper:358.0
Total weight Glass:653.0
Total weight Cardboard:174.0
*/