Java compilation error cannot find symbol in implementing interface
<p>The following error showed while I was compiling my Java class:</p>

<blockquote>
  <p>Radius.java:27: error: cannot find symbol<br>
      public class Radius implements B,C<br>
                                     ^
        symbol: class B<br>
      Radius.java:27: error: cannot find symbol<br>
      public class Radius implements B,C<br>
                                       ^
        symbol: class C<br>
      2 errors</p>
</blockquote>

<p>The Java class in question:</p>

<pre><code>class A
{
    int radius;
    interface B
    {
        public String displayRadius();
    }

    interface C
    {
        public String displayArea();
    }

    public void displayRadius()
    {
        radius=2;
        System.out.println("Radius : "+radius);
    }

    public void displayArea()
    {
        double area;
        area=3.14*radius*radius;
        System.out.println("Area :"+area);
    }
}

public class Radius implements B,C
{
    public static void main(String args[])
    {
        A ob=new A();
        ob.displayRadius();
        ob.displayArea();
    }
}
</code></pre>

<p>What is the problem?</p>