ItemElement.java

package com.journaldev.design.visitor;

public interface ItemElement {

 public int accept(ShoppingCartVisitor visitor);
}

package com.journaldev.design.visitor;

public class Book implements ItemElement {

 private int price;
 private String isbnNumber;

 public Book(int cost, String isbn){
 this.price=cost;
 this.isbnNumber=isbn;
 }

 public int getPrice() {
 return price;
 }

 public String getIsbnNumber() {
 return isbnNumber;
 }

 @Override
 public int accept(ShoppingCartVisitor visitor) {
 return visitor.visit(this);
 }

}

package com.journaldev.design.visitor;

public class Fruit implements ItemElement {

 private int pricePerKg;
 private int weight;
 private String name;

 public Fruit(int priceKg, int wt, String nm){
 this.pricePerKg=priceKg;
 this.weight=wt;
 this.name = nm;
 }

 public int getPricePerKg() {
 return pricePerKg;
 }

 public int getWeight() {
 return weight;
 }

 public String getName(){
 return this.name;
 }

 @Override
 public int accept(ShoppingCartVisitor visitor) {
 return visitor.visit(this);
 }

}

package com.journaldev.design.visitor;

public interface ShoppingCartVisitor {

 int visit(Book book);
 int visit(Fruit fruit);
}

package com.journaldev.design.visitor;

public class ShoppingCartVisitorImpl implements ShoppingCartVisitor {

 @Override
 public int visit(Book book) {
 int cost=0;
 //apply 5$ discount if book price is greater than 50
 if(book.getPrice() > 50){
  cost = book.getPrice()-5;
 }else cost = book.getPrice();
 System.out.println("Book ISBN::"+book.getIsbnNumber() + " cost ="+cost);
 return cost;
 }

 @Override
 public int visit(Fruit fruit) {
 int cost = fruit.getPricePerKg()*fruit.getWeight();
 System.out.println(fruit.getName() + " cost = "+cost);
 return cost;
 }

}

package com.journaldev.design.visitor;

public class ShoppingCartClient {

 public static void main(String[] args) {
 ItemElement[] items = new ItemElement[]{new Book(20, "1234"),new Book(100, "5678"),
  new Fruit(10, 2, "Banana"), new Fruit(5, 5, "Apple")};

 int total = calculatePrice(items);
 System.out.println("Total Cost = "+total);
 }

 private static int calculatePrice(ItemElement[] items) {
 ShoppingCartVisitor visitor = new ShoppingCartVisitorImpl();
 int sum=0;
 for(ItemElement item : items){
  sum = sum + item.accept(visitor);
 }
 return sum;
 }

}

Book ISBN::1234 cost =20
Book ISBN::5678 cost =95
Banana cost = 20
Apple cost = 25
Total Cost = 160