Builder design pattern

This is another creational design pattern. Just think about the StringBuilder. If you create a StringBuilder object, you can append strings one by one to the same StringBuilder object.

                 StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("Java").append("Foundation");

This is the functionality of the builder pattern. There are a few ways to implement the builder pattern.

Using constructor

	package com.app.designPatterns.builder1;
	public class BuilderApp {
	public static void main(String[] args) {
	Phone iphone = new PhoneBuilder().setModel("Apple").setOs("IOS").buildPhone();
	System.out.println(iphone);
	Phone androidPhone = new PhoneBuilder().setModel("Nokia").setOs("Android").setCamera("32MP").buildPhone();
	System.out.println(androidPhone);
	}
	}

view rawBuilderApp.java hosted with ❤ by GitHub

	package com.app.designPatterns.builder1;
	public class Phone {
	private String model;
	private String os;
	private Integer price;
	private String camera;
	public Phone(String model, String os, Integer price, String camera) {
	super();
	this.model = model;
	this.os = os;
	this.price = price;
	this.camera = camera;
	}
	@Override
	public String toString() {
	return "Phone{" +
	"model='" + model + '\'' +
	", os='" + os + '\'' +
	", price=" + price +
	", camera='" + camera + '\'' +
	'}';
	}
	}

view rawPhone.java hosted with ❤ by GitHub

	package com.app.designPatterns.builder1;
	public class PhoneBuilder {
	private String model;
	private String os;
	private Integer price;
	private String camera;
	public PhoneBuilder setModel(String model) {
	this.model = model;
	return this;
	}
	public PhoneBuilder setOs(String os) {
	this.os = os;
	return this;
	}
	public PhoneBuilder setPrice(Integer price) {
	this.price = price;
	return this;
	}
	public PhoneBuilder setCamera(String camera) {
	this.camera = camera;
	return this;
	}
	public Phone buildPhone() {
	return new Phone(model, os, price, camera);
	}
	}

view rawPhoneBuilder.java hosted with ❤ by GitHub

Using inner class

	package com.app.designPatterns.builder3;
	public class Car {
	private final String make;
	private final Integer price;
	private final Boolean sunroof;
	private final Boolean alloyWheels;
	private final Boolean cruiseControl;
	private final Boolean electricSeats;
	public Car(CarBuilder carBuilder){
	this.make = carBuilder.make;
	this.price = carBuilder.price;
	this.sunroof = carBuilder.sunroof;
	this.alloyWheels = carBuilder.alloyWheels;
	this.cruiseControl = carBuilder.cruiseControl;
	this.electricSeats = carBuilder.electricSeats;
	}
	static class CarBuilder{
	private String make;
	private Integer price;
	private Boolean sunroof;
	private Boolean alloyWheels;
	private Boolean cruiseControl;
	private Boolean electricSeats;
	public Car build(){
	return new Car(this);
	}
	public CarBuilder(String make){
	this.make = make;
	}
	public CarBuilder price(Integer price){
	this.price = price;
	return this;
	}
	public CarBuilder sunroof(Boolean sunroof){
	this.sunroof = sunroof;
	return this;
	}
	public CarBuilder alloyWheels(Boolean alloyWheels){
	this.alloyWheels = alloyWheels;
	return this;
	}
	public CarBuilder cruiseControl(Boolean cruiseControl){
	this.cruiseControl = cruiseControl;
	return this;
	}
	public CarBuilder electricSeats(Boolean electricSeats){
	this.electricSeats = electricSeats;
	return this;
	}
	}
	@Override
	public String toString() {
	return "Car{" +
	"make='" + make + '\'' +
	", price=" + price +
	", sunroof='" + sunroof + '\'' +
	", alloyWheels='" + alloyWheels + '\'' +
	", cruiseControl='" + cruiseControl + '\'' +
	", electricSeats='" + electricSeats + '\'' +
	'}';
	}
	}

view rawCar.java hosted with ❤ by GitHub

	package com.app.designPatterns.builder3;
	public class CarApp {
	public static void main(String[] args) {
	Car.CarBuilder priusBuilder = new Car.CarBuilder("Prius");
	Car prius = priusBuilder.price(200).sunroof(true).alloyWheels(true).cruiseControl(true).electricSeats(true).build();
	System.out.println(prius);
	Car.CarBuilder priusCBuilder = new Car.CarBuilder("Prius C");
	Car priusC = priusCBuilder.price(180).sunroof(true).alloyWheels(true).cruiseControl(false).build();
	System.out.println(priusC);
	Car.CarBuilder priusVBuilder = new Car.CarBuilder("Prius V");
	Car priusV = priusVBuilder.price(180).alloyWheels(true).build();
	System.out.println(priusV);
	}
	}

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The second method is the best way to implement the builder pattern. 

Advantages of the Builder pattern

• The builder pattern solves the complex Telescopic constructors
• Make it easy to create objects that have many attributes.

Disadvantages of the Builder pattern

• Code looks complex
• Object creation depends on the Builder class

Use of Builder design pattern in Java core

• StringBuilder
• StringBuffer
• JsonObjectBuilder
• Calendar in Java 8
• Locale in Java 7
• Stream API in Java 8