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I likeThatMeow
Asked: 2020-09-22 07:53:23 +0800 CST 2020-09-22 07:53:23 +0800 CST

How to print class type data?

  • 772

In the method queueAnalysis, when I command to print System.out.println("Original: " + queue + "\n");, System.out.println("colados: " + names + "\n");and System.out.println("Cola final: " +queue);, it gives me as output direcciones de memoria, nulland direcciones de memoria, I already tried to apply a iteratorand apply a class type casting Customerbut even so it continues to give memory addresses as output. Why?,

How can I fix the problem?

class Customer {

String name;
int ticket;

Customer(String name, int ticket) {
    this.name = name;
    this.ticket = ticket;

}

String getName() {
    return name;

}

int getTicket() {
    return ticket;
}
}

public class Main {

public static void main(String[] args) {
    Queue<Customer> queue = new LinkedList<>();
    queue.add(new Customer("a1", 1));
    queue.add(new Customer("a2", 2));
    queue.add(new Customer("a3", -1));
    queue.add(new Customer("a4", -1));

    queueAnalysis(queue);
}

public static void queueAnalysis(Queue<Customer> queue) {

    System.out.println("Original: " + queue + "\n");
    String names[] = null;
    int cant = 0;
    int tam = queue.size();

    for (int i = 0; i < tam; i++) {
        if (queue.peek().getTicket() == -1) {
            names[i] = queue.peek().getName();
            cant++;
            queue.poll();


        }

    }
    System.out.println("colados: " + names + "\n");
    System.out.println("Cola final: " +queue); 

    //Customer c;
    for (Iterator it = queue.iterator(); it.hasNext();) {
        System.out.println((Customer) it.next());
    }

}

}
java

3 Answers

  1. You can't print an arrayList directly or a vector:

    for( Customer c: queue ){
  System.out.println( "Original: " + c.getName( ) + "" + c.getTicket( ));
}
    • 2

  2. If what you want is to show the name of the objects or something else, simply override the ToString() method of the Customer class.

    public class Customer {

    String name;
    int ticket;

    public Customer(String name, int ticket) {
        this.name = name;
        this.ticket = ticket;

    }

    String getName() {
        return name;

    }

    int getTicket() {
        return ticket;
    }


    @Override
    public String toString(){
        return getName()+ "-" + getTicket();        
    }
}
    • 2
  3. Best Answer

    In addition to the answer given by @Edu3D, you must change the way you get the data from the queues and the filafinal one, this is because you are not accessing the queue by indices and when you do peek()or poll()it is always on the object that is in the headde the row, here I modify the method

    public static void queueAnalysis(Queue<Customer> queue) {
  System.out.println("Original: " + queue + "\n");
  Queue<Customer> colados = new LinkedList<>();
  Queue<Customer> noColados = new LinkedList<>();
  while(!queue.isEmpty()){
    if (queue.peek().getTicket() == -1) {
      colados.add(queue.poll());
    }else{
      noColados.add(queue.poll());
    }
  }
  System.out.println("colados: " + colados + "\n");
  System.out.println("Cola final: " + noColados);
  //Customer c;
  for (Iterator it = queue.iterator(); it.hasNext();) {
    System.out.println((Customer) it.next());
  }
}

    This only works if you make the changes mentioned by @Edu3D to override the toString()class methodCustomer

    public class Customer {
  String name;
  int ticket;

  public Customer(String name, int ticket) {
    this.name = name;
    this.ticket = ticket;
  }
  String getName() {
    return name;
  }
  int getTicket() {
    return ticket;
  }

  @Override
  public String toString(){
    return getName()+ "-" + getTicket();        
  }
}
    • 2