<h2 id="heading-functional-interface">Functional Interface</h2>
<ul>
<li>As we know interface is a blueprint of a class. It has static constants and abstract methods. A Functional Interface is an interface that only has one abstract method. Interface methods are by default public, and abstract. Thus it is not required to add <code>public abstract int sum(int a, int b);</code> In java, Runnable is a Functional Interface that has only a <code>run</code> method.</li>
</ul>
<pre><code class="lang-java">@FunctionalInterface
interface GetSummation{
 int sum(int a, int b);
}
</code></pre>

## ***Functional Interface***

* As we know interface is a **blueprint of a class.** It has static constants and abstract methods. A Functional Interface is an interface that **only has one** abstract method. Interface methods are by default **public, and abstract.** Thus it is not required to add `public abstract int sum(int a, int b);` In java, **Runnable** is a Functional Interface that has only a `run` method.
    

```java
@FunctionalInterface
interface GetSummation{
    int sum(int a, int b);
}
```