title: why do we need interface in java which provides just a method signature
body: <p>I am literally confused with the java with regard to interface : following is the interface I have :</p>
  
  <pre><code>interface shape
   {
       public   String baseclass="shape";
  
       public void Draw();     
  
   }
  </code></pre>
  
  <p>likewise I can have any number of interface and another class can implement any number be interface but the implementing class has to implement all the method provided by the interface.</p>
  
  <p>the only advantage I could see is having some common properties and share them across class.</p>
  
  <p>Instead of implementing interface the class can declare the method and use it and this also will work fine.</p>
  
  <p>so why do wee need interface in java? even if it is for multiple inheritance, the interface is not having implementation but the method signature alone.</p>
  
  <p>I am really confused with these and of course the famous abstract class too.</p>
  
  <p>thanks.</p>