Question

how do I write this function to check if it is close?

below is checking if the function is open. I want to write another if then statement to check when that function is closed and when the queue is empty. You can use any variables or declaration as a example to show me how it is done.

if (tx.isSenderStreamOpen())

{

}

Answer 1

/**
* Top level class available for the Client. In this example Main class is the client
*/
import java.util.Queue;
import java.util.LinkedList;;

public class Transaction {
   /**
   * Data member of type SenderStream
   */
   private SenderStream senderStream;
  
   /**
   * Opens the SenderStream with empty queue
   */
   public void open(){
       senderStream = new SenderStream();
   }
  
   /**
   * Opens the SenderStream with Queue elements
   * @param queue
   */
   public void open(Queue queue){
       senderStream = new SenderStream(queue);
   }
  
   /**
   * Closes the SenderStream
   */
   public void close(){
       senderStream = null;
   }
  
   /**
   * Checks whether a SenderStream is open or not
   * @return true or false
   */
   public boolean isSenderStreamOpen(){
       if(senderStream!=null)
           return true;
       return false;
   }
  
   /**
   * Checks whether the queue of empty or not. If SenderStream is closed, throws SenderStreamException
   * @return true or false
   * @throws SenderStreamException
   */
   public boolean isSenderStreamEmpty() throws SenderStreamException{
       if(senderStream==null)
           throw new SenderStreamException("Sender Stream is closed.");
       if(senderStream.getQueue().size()==0)
           return true;
       return false;
   }

}

/**
* SenderStream class with Queue
*
*/
class SenderStream{
   /**
   * This queue for the element
   */
   private Queue queue;

   /**
   * Queue constructor
   * @param queue
   */
   public SenderStream(Queue queue) {
       this.queue = queue;
   }

   /**
   * Queue default constructor
   */
   public SenderStream() {
       this.queue = new LinkedList<>();
   }

   /**
   * Retrieve the SendStream Queue
   * @return
   */
   public Queue getQueue() {
       return queue;
   }

   /**
   * Sets the SendStream Queue
   * @param queue
   */
   public void setQueue(Queue queue) {
       this.queue = queue;
   }
  
}

/**
* Exception class for throwing ClosedSenderStream exception
*
*/
class SenderStreamException extends Exception{

   public SenderStreamException(String message) {
       super(message);
   }
}

//Main class

public class Main {

   public static void main(String[] args) {
       Transaction tx = new Transaction();

       //Without opening the SenderStream
       if(tx.isSenderStreamOpen())
           System.out.println("Sender Stream is open");
       else
           System.out.println("Sender Stream is closed");
       //Output => Sender Stream is closed
      
       try {
           if(tx.isSenderStreamEmpty()){
               System.out.println("Sender Stream is empty");
           }
       } catch (SenderStreamException e1) {
           System.out.println("Sender Stream is closed");
           e1.printStackTrace();
       }
       //Outptut => Sender Stream is closed, followed by Exception
      
      
       //Openning the Sender Stream
       tx.open();
      
       if(tx.isSenderStreamOpen())
           System.out.println("Sender Stream is open");
       else
           System.out.println("Sender Stream is closed");
       //Output => Sender Stream is open
      
       try {
           if(tx.isSenderStreamEmpty()){
               System.out.println("Sender Stream is empty");
           }
       } catch (SenderStreamException e1) {
           System.out.println("Sender Stream is closed");
           e1.printStackTrace();
       }
       //Output => Sender Stream is empty
       tx.close();

   }

}

//Output

Sender Stream is closed
Sender Stream is closed
com.sandeep.SenderStreamException: Sender Stream is closed.
   at com.sandeep.Transaction.isSenderStreamEmpty(Transaction.java:54)
   at com.sandeep.TransactionMain.main(TransactionMain.java:16)
Sender Stream is open
Sender Stream is empty