title: Meaning of new Class(...){{...}} initialization idiom
body: <p>What does <code>{{ ... }}</code> block mean in the following code?</p>
  
  <pre><code>class X {
  
      private Y var1;
  
      private X() {
          Z context = new Z(new SystemThreadPool()) {{
              var1 = new Y();
          }};
      }
  
  }
  </code></pre>