title: What does "this()" method mean?
body: <p>I ran into this block of code, and there is this one line I don't quit understand the meaning or what it is doing.</p>
  
  <pre><code>public Digraph(In in) {
      this(in.readInt()); 
      int E = in.readInt();
      for (int i = 0; i &lt; E; i++) {
          int v = in.readInt();
          int w = in.readInt();
          addEdge(v, w); 
      }
  }
  </code></pre>
  
  <p>I understand what <code>this.method()</code> or <code>this.variable</code> are, but what is <code>this()</code>? </p>