Factory Method

Factory Method is the way of delegating the object creation logic to the client.

Real world example

Consider the case of a bank. It's possible for both local and foreigner to open a bank account. So the bank has to delegate the register account steps to them.

Example

BankAccount interface and implementations

interface BankAccount {
  public void registerAccount();
}
 
class LocalAccount implements BankAccount {
  public void registerAccount() {
    System.out.println("Registering account for local.");
  }
}
 
class ForeigneAccount implements BankAccount {
  public void registerAccount() {
    System.out.println("Registering account for foreigner.");
  }
}

Bank

abstract class Bank {
  abstract protected BankAccount makeBankAccount();
  
  public void openBankAccount() {
    BankAccount bankAccount = this.makeBankAccount();
    bankAccount.registerAccount();
  }
}

Any child can extend it and provide the required BankAccount

class LocalBankAccount extends Bank {
  protected BankAccount makeBankAccount() {
    return new LocalAccount();
  }
}
 
class ForeigneBankAccount extends Bank {
  protected BankAccount makeBankAccount() {
    return new ForeigneAccount();
  }
}

It can be used as

LocalBankAccount local = new LocalBankAccount();
local.openBankAccount(); // Output: Registering account for local
 
ForeigneBankAccount roreigner = new ForeigneBankAccount();
roreigner.openBankAccount(); // Output: Registering account for foreigner

Simple Factory