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copied!<p>Yes, Java is pass-by-reference with objects, definitely.</p> <p>But what you're doing is that your <code>Writer</code> assumes that your <code>GUI</code> is written in stone, meaning that it will always have a property called <code>textBox</code>. </p> <p>Just by the look of things, <code>Writer</code> should not be responsible for accessing and manipulating the properties of <code>GUI</code>. If you change what's in your <code>GUI</code>, you will also need to recode the <code>Writer</code> class.</p> <p>You could recode your <code>Writer</code> to merely send a message to the <code>GUI</code> because its responsibility is just to tell <code>GUI</code> what to write, not how to write it. Then leave it upto the <code>GUI</code> to process that message:</p> <pre><code>class GUI { Writer w; void initGUI() { w = new Writer(this); } void ReceiveMessage(string message) { this.textBox.text = message; } } </code></pre> <p>Your <code>Writer</code> class:</p> <pre><code>class Writer { GUI ui; public Write(GUI ui) { this.ui = ui; // Don't send the message in the constructor. } // The program calls this function with whatever text the user enters. public void SendMessage(string message) { ui.ReceiveMessage(message); // Writer no longer depends on ui to have a textbox Element. } } </code></pre> <p>The above code could be improved with an interface. This way, you can pass anything to your writer that needs to know how to receive a message:</p> <pre><code>interface IMessageReceiver { void ReceiveMessage(string message); } </code></pre> <p>Now, your <code>GUI</code> becomes an IMessageReceiver:</p> <pre><code>class GUI implements IMessageReceiver { Writer w; void initGUI() { w = new Writer(this); } public void ReceiveMessage(string message) { this.textBox.text = message; } } </code></pre> <p><code>Writer</code> class now:</p> <pre><code>class Writer { IMessageReceiver receiver; public Write(MessageReceiver receiver) { this.receiver = receiver; // Don't send the message in the constructor. } // The program calls this function with whatever text the user enters. public void SendMessage(string message) { receiver.ReceiveMessage(message); } } </code></pre> <p>The difference here is that <code>Writer</code> will no longer care whether or not it's a <code>GUI</code>. It will take any object as long as it is an <code>IMessageReceiver</code> that knows how to receive messages.</p> <p>If you're not familiar with interfaces, do some reading/research on it. They are extremely handy, if not, vital!</p>

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