title: Declaration vs. Instantiation
body: <p>Comming from Java, I have difficulty with the code below.
  In my understanding b is just declared on line 3 but not instantiated.</p>
  
  <p>What would be the text book way of creating an instance of B in class A?</p>
  
  <pre><code>class A {
    private:
      B b;
    public:
      A() { 
        //instantiate b here?
      }
  };
  </code></pre>
  
  <p>Edit: What if B does not have a default constructor?</p>