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    <p>In Scala the parameters of the constructor become public attributes of the class if declared as a <code>var</code> or <code>val</code>.</p> <pre><code>scala&gt; class Point(val x: Int, val y: Int){} defined class Point scala&gt; val point = new Point(1,1) point: Point = Point@1bd53074 scala&gt; point.x res0: Int = 1 scala&gt; point.y res1: Int = 1 </code></pre> <p><strong>Edit to answer the question in comments</strong> "if they were private fields, shouldn't my first code snipped after the edit have worked?"</p> <p>The constructor <code>class Point(x: Int, y: Int)</code> generates <em>object-private</em> fields which only allow methods of the <code>Point</code> class to access the fields <code>x</code> and <code>y</code> not other objects of type <code>Point</code>. <code>that</code> in the <code>+</code> method is another object and is not allowed access with this definition. To see this in action define add a method <code>def xy:Int = x + y</code> which does not generate a compile error.</p> <p>To have <code>x</code> and <code>y</code> accessible to the class use a <em>class-private</em> field which is as follows:</p> <pre><code>class Point(private val x: Int, private val y: Int) { def +(that: Point): Point = new Point(this.x + that.x, this.y + that.y) } </code></pre> <p>Now they are not accessible outside of the class:</p> <pre><code>scala&gt; val point = new Point(1,1) point: Point = Point@43ba9cea scala&gt; point.x &lt;console&gt;:10: error: value x in class Point cannot be accessed in Point point.x ^ scala&gt; point.y &lt;console&gt;:10: error: value y in class Point cannot be accessed in Point point.y </code></pre> <p>You can see this in action by using <code>scalac -Xprint:parser Point.scala</code>.</p>
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    1. COOh, thanks! If i don't set them to val, they are just parameters to the constructor then, is that it? What if I wanted them to be private attributes?
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    2. COSee http://www.scala-lang.org/node/539#comment-650 for how to make the arguments private.
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    3. COIf you don't add `var` or `val` they are parameters to the constructor and private fields in the class. Also see the section "Constructors in Scala" in the book http://ofps.oreilly.com/titles/9780596155957/BasicObjectOrientedProgramming.html
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