Bank Maker-Checker Refactoring (Java)

1_README.md

Bank Maker-Checker Refactoring (Java)

ApprovalStrategy.java

package bank;

public interface ApprovalStrategy {
  boolean approve(Transactions ts);
  
  public static ApprovalStrategy valueOf(Transactions transactions) {
    if (transactions.totalValue() < 100000d)
      return new SingleMakerChecker(new Maker(), new Checker());
    else
      return new DoubleMakerChecker(new Maker(), new Checker(), new Checker());
  }
}

Checker.java

package bank;

class Checker { }

DoubleMakerChecker.java

package bank;

class DoubleMakerChecker implements ApprovalStrategy {
  public DoubleMakerChecker(Maker m, Checker c1, Checker c2) { }

  public boolean approve(Transactions ts) {
    return true;
  }
}

Main.java

package bank;

import java.util.List;

public class Main {
  public static List<Transaction> createTransactions() {
    Transaction t1 = new Transaction() {
         public boolean approve() { return true; }
         public boolean reject(String reason) { return false; }
    };
    return Arrays.asList(t1, t1);
  }
    
  public static void main(String[] args) {
    
    Transactions transactions = new Transactions(createTransactions());
    ApprovalStrategy approvalStrategy = ApprovalStrategy.valueOf(transactions);
    transactions.approve(approvalStrategy);
  }
}

Maker.java

package bank;

class Maker { }

SingleMakerChecker.java

package bank;

class SingleMakerChecker implements ApprovalStrategy {
  public SingleMakerChecker(Maker m, Checker c) { }

  public boolean approve(Transactions ts) {
    return true;
  }
}

Transaction.java

package bank;

public interface Transaction { 
  public boolean approve();
  public boolean reject(String reason);
}

Transactions.java

package bank;

import java.util.List;

public class Transactions {
  private final List<Transaction> transactions;
  public Transactions(List<Transaction> transactions) { 
    this.transactions = transactions;
  }

  public boolean approve(ApprovalStrategy aps) {
    return aps.approve(this);
  }
  
  public Double totalValue() { 
    // This will loop through all transactions and add all transactions value.  
    // This is hard-coded for purpose of this example.
    return 1000000d; 
  }  
}