// TransactionManager.java

public abstract class TransactionManager {
 private String separator;
 
 public TransactionManager(String separator) {
 this.separator = separator;
 }
 
 public abstract void writeTransaction(String result);
 
 public Transaction startTransaction()
 {
 Transaction transaction = new Transaction(System.currentTimeMillis());
 return transaction;
 }
 
 public void endTransaction(Transaction t) {
 long processingTime = System.currentTimeMillis() - t.getStartTime();
 
 StringBuilder logBuilder = new StringBuilder();
 logBuilder.append(t.getStartTime());
 // Notice the use of this.separator
 logBuilder.append(this.separator);
 logBuilder.append(processingTime);
 logBuilder.append(this.separator);
 logBuilder.append(t.getData());
 
 String result = logBuilder.toString();
 writeTransaction(result);
 }
}

public class TransactionManagerFS extends TransactionManager{
 
 // The IDE forces you to implement constructor.
 public TransactionManagerFS(String separator) {
 super(separator);
 }
 
 @Override
 public void writeTransaction(String result) {
 System.out.println("The following transaction has just finished: " );
 System.out.println(result);
 }
}

public static void main(String[] args) throws InterruptedException {
 // we pass the separator explicitly in the constructor
 TransactionManager transactionManager = new TransactionManagerFS(",");
 Transaction transaction = transactionManager.startTransaction();
 transaction.setData("This is a test transaction !!");
 Thread.sleep(1500);
 transactionManager.endTransaction(transaction);
 }

The following transaction has just finished: 
1502179140689,1501,This is a test transaction !!

public abstract class TransactionManager {
 
 public abstract String getSeperator();
 public abstract void writeTransaction(String result);
 
 public Transaction startTransaction()
 {
 Transaction transaction = new Transaction(System.currentTimeMillis());
 return transaction;
 }
 
 public void endTransaction(Transaction t) {
 long processingTime = System.currentTimeMillis() - t.getStartTime();
 
 StringBuilder logBuilder = new StringBuilder();
 logBuilder.append(t.getStartTime());
 // Notice the use of getSeparator()
 logBuilder.append(getSeperator());
 logBuilder.append(processingTime);
 logBuilder.append(getSeperator());
 logBuilder.append(t.getData());
 
 String result = logBuilder.toString();
 writeTransaction(result);
 }
}

public class TransactionManagerFS extends TransactionManager{
 
 @Override
 public String getSeperator() {
 return ",";
 }
 
 @Override
 public void writeTransaction(String result) {
 System.out.println("The following transaction has just finished: " );
 System.out.println(result);
 }
}

public static void main(String[] args) throws InterruptedException {
 // The separator is defined implicitly using getSeparator() method of the manager
 TransactionManager transactionManager = new TransactionManagerFS();
 Transaction transaction = transactionManager.startTransaction();
 transaction.setData("This is a test transaction !!");
 Thread.sleep(1500);
 transactionManager.endTransaction(transaction);
 }

The following transaction has just finished: 
1502179140689,1501,This is a test transaction !!