Dr. Javier Gonzalez-Sanchez javiergs@calpoly.edu www.javiergs.info o ffi ce: 14 -227 CSC 305 Individual Software Design and Development Lecture 13. Builder + Chain of Responsibilities

Previously

GoF Patterns 3

Fluent-Builder

Fluent-Builder • The Fluent Builder is a builder whose design relies on method chaining. In doing so, it a ims to promote code legibility. 5

UserPro f ile class UserProfileBuilder { private final String username; private String email = "Not provided"; private String phoneNumber = "Not provided"; private String address = "Not provided"; private int age = 18; public UserProfileBuilder(String username) { this.username = username; } public UserProfileBuilder email(String email) { this.email = email; return this; } 6

UserPro f ile public UserProfileBuilder phoneNumber(String phoneNumber) { this.phoneNumber = phoneNumber; return this; } public UserProfileBuilder address(String address) { this.address = address; return this; } public UserProfileBuilder age(int age) { if (age < 13) throw new IllegalArgumentException("Age must be 13 or older."); this.age = age; return this; } public UserProfile build() { return new UserProfile(username, email, phoneNumber, address, age); } } 7

UserPro f ile class UserProfile { private final String username; private final String email; private final String phoneNumber; private final String address; private final int age; public UserProfile(String username, String email, String phoneNumber, String address, int age) { this.username = username; this.email = email; this.phoneNumber = phoneNumber; this.address = address; this.age = age; } public String toString() { return String.format( "UserProfile: { Username: %s, Email: %s, Phone: %s, Address: %s, Age: %d }", username, email, phoneNumber, address, age ); } } 8

FluentBuilderExample public class FluentBuilderExample { public static void main(String[] args) { // Example 1: Creating a user in a single line UserProfile user1 = new UserProfileBuilder("alice123") .email("alice@example.com") .phoneNumber("555-1234") .address("123 Main St, NY") .age(25) .build(); // Example 2: Building the object step by step UserProfileBuilder builder = new UserProfileBuilder("bob456"); builder.email("bob@example.com").phoneNumber("555-5678"); UserProfile user2 = builder.address("456 Elm St, LA").age(30).build(); System.out.println(user1); System.out.println(user2); } } 9

Another Fluent-Builder

Fluent-Builder import java.awt.*; public class Client { public static void main(String[] args) { FluentBuilder builder = new BoxFluentBuilder() .setColor(Color.RED) .setSize(20) .setX(10) .setY(20); Product box = ((BoxFluentBuilder)builder).get(); } } 11

Fluent-Builder import java.awt.Color; public interface FluentBuilder { public Builder setColor(Color color); public Builder setSize(int size); public Builder setX(int x); public Builder setY(int y); } 12

Fluent-Builder import java.awt.*; public class BoxFluentBuilder implements FluentBuilder { private Color color; private int size, x, y; public Builder setColor (Color color) { this.color = color; return this; } public Builder setSize(int size) { this.size = size; return this; } public Builder setX(int x) { this.x = x; return this; } public Builder setY(int y) { this.y = y; return this; } public Box get() { return new Box (color, size, x, y); } } 13

Chain of Responsibility

Chain of Responsibility • Avoid coupling the sender of a request to its receiver by giving more th a n one object a ch a nce to h a ndle the request. 15

Chain of Responsibility 16

Chain of Responsibility vs Composite vs Decorator 17

Chain of Responsibility // Setup Chain of Responsibility Handler h1 = new ConcreteHandler2(); Handler h2 = new ConcreteHandler2(); Handler h3 = new ConcreteHandler1(); h1.setSuccessor(h2); h2.setSuccessor(h3); // Generate and process request int[] requests = { 2, 5, 14, 22, 18, 3, 27, 20 }; foreach (int i=0; i

Handler abstract class Handler { public abstract void handleRequest(int request); } class ConcreteHandler1 extends Handler { public void handleRequest(int request) { if (request >= 0 && request < 10) { // code here… } else { // nothing can be done :( } } } 19

Handler class ConcreteHandler2 extends Handler { protected Handler successor; public void setSuccessor(Handler successor) { this.successor = successor; } public override void handleRequest(int request) { if (request >= 10 && request < 20) { // code here } else if (successor != null) { successor.handleRequest(request); } } } 20

Example 21 The Logger Case

Questions 22

Lab

Example 24 Lab Instructions Provided on Paper

CSC 305 Individual Software Design and Development Javier Gonzalez-Sanchez, Ph.D. javiergs@calpoly.edu Winter 2025 Copyright. These slides can only be used as study material for the class CSC305 at Cal Poly. They cannot be distributed or used for another purpose.