Sample implementation of the Builder design pattern

In the following code example, I am going to create an Account class that has AccountBuilder as an inner class. The AccountBuilder class has a method to create an instance of this class:

    package com.packt.patterninspring.chapter2.builder.pattern; 
    public class Account { 
      private String accountName; 
      private Long accountNumber; 
      private String accountHolder; 
      private double balance; 
      private String type; 
      private double interest; 
      private Account(AccountBuilder accountBuilder) { 
         super(); 
         this.accountName = accountBuilder.accountName; 
         this.accountNumber = accountBuilder.accountNumber; 
         this.accountHolder = accountBuilder.accountHolder; 
         this.balance = accountBuilder.balance; 
         this.type = accountBuilder.type; 
         this.interest = accountBuilder.interest; 
      } 
      //setters and getters 
       public static class AccountBuilder { 
         private final String accountName; 
         private final Long accountNumber; 
         private final String accountHolder; 
         private double balance; 
         private String type; 
         private double interest; 
         public AccountBuilder(String accountName, 
            String accountHolder, Long accountNumber) { 
            this.accountName = accountName; 
            this.accountHolder = accountHolder; 
            this.accountNumber = accountNumber; 
         } 
         public AccountBuilder balance(double balance) { 
            this.balance = balance; 
            return this; 
         } 
         public AccountBuilder type(String type) { 
            this.type = type; 
            return this; 
         } 
         public AccountBuilder interest(double interest) { 
            this.interest = interest; 
            return this; 
         } 
         public Account build() { 
            Account user =  new Account(this); 
            return user; 
         } 
       } 
       public String toString() { 
       return "Account [accountName=" + accountName + ", 
          accountNumber=" + accountNumber + ", accountHolder=" 
          + accountHolder + ", balance=" + balance + ", type="
          + type + ", interest=" + interest + "]"; 
       } 
    } 

AccountBuilderTest.java is a demo class that we will use to test the design pattern. Let's look at how to build an Account object by passing the initial information to the object:

     package com.packt.patterninspring.chapter2.builder.pattern; 
     public class AccountBuilderTest { 
       public static void main(String[] args) { 
         Account account = new Account.AccountBuilder("Saving
            Account", "Dinesh Rajput", 1111l) 
              .balance(38458.32) 
              .interest(4.5) 
              .type("SAVING") 
              .build(); 
         System.out.println(account); 
       } 
     } 

You can test this file and see the output on the console: