How to solve problem with action listener?

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Java

C++98

    private void DequeueActionPerformed(java.awt.event.ActionEvent evt) {                                        
        a.dequeue();
      
        if(a.count<=0){
         JOptionPane.showMessageDialog(this, "This is underflow", "Message", EXIT_ON_CLOSE);
        } else{
         JOptionPane.showMessageDialog(this, "Dequeued: "+a.Queue[a.count].toString(), "Message", EXIT_ON_CLOSE);
        }
        refresh();
}

private void EnqueueActionPerformed(java.awt.event.ActionEvent evt) {                                        

        a.enqueue(jTextFieldElement.getText());
        jTextFieldElement.setText("");
        if(a.count==a.size ||a.count < (size-1)){
         JOptionPane.showMessageDialog(this, "This is overflow", "Message", EXIT_ON_CLOSE);
        }
        refresh();
       
        
    }       

 public boolean enqueue(Object element)
{
    if( count==size  )
    return false;

    Queue[count] = element;
    count++;

    return true;

}

public Object dequeue()
{
    if(count==0 )
    return false;

    count--;
    return Queue[count];
}

What I have tried:

I have problem with these codes. When i enter size=2,size will be 2. And when i enter 1 number,it is working correctly,but when i enter 2nd number ,it is working wrongly,it add this number ,but it must not add it and it must show "overflow " message.becuase for queues the last place must be empty,it must not add number to the last place of array.how can i solve this?what is wrong with my code?


and the 2nd problem.

the second problem is related with "underflow".
when i enter 2 for size,then i enter 2number.and then when i dequeue these numbers,after 1st number it shows "underflow" message.but it must show this message when array is empty and i want to dequeue it.

Sorry for my english.
and please help for solving these problems.

Thanks in advance.