title: How to create two interfaces to a Java class one read-only, one read-write?
body: <p>I'm writing a game engine in Java for a two player card game for which my students are going to write AI players.</p>
  
  <p>The AI players will take turns playing cards onto their 'field' a part of the 'table' in front of them.  They can attack with a card from their field a card in the other player's field.  Cards may be face up or face down.</p>
  
  <p>The GameEngine class allows an AI player to take his/her turn by calling the GamePlayer.TakeTurn(GameEngine eng) method.  The player can ask the game engine for the defending player's field so the player can make decisions based on the number of cards there and which ones are face up.  Let's say this method is GameEngine.GetDefendingField()</p>
  
  <p>Now, I want to make sure that the attacking player cannot modify the defending player's field or the cards in the defending player's field and that the attacking player can only identify the face up cards in the defending players field.</p>
  
  <p>I have classes for Card, Field (an ArrayList of Cards), GamePlayer and GameEngine.  Is there any way to create an interface for Field so that the GameEngine can return the defending player's field without the attacking player being able to change it? and without the attacking player being able to recast the defending player's field into something that can be changed.</p>
  
  <p>Can I have GameEngine.GetDefendingField() return a read-only interface to a Field that cannot be recast to a Field?</p>
  
  <p>tia,</p>
  
  <p>Sh-</p>