Lambda expressions and functional interfaces

Lambda expressions are essential in functional programming. Lambda expressions are constructs that exist in a standalone fashion and not as a part of any class. One particular scenario where Lambda expressions can be used is while creating classes which consist of just a single method. Lambda expressions, in this case, help to be an alternative to anonymous classes (classes without names), which might not be feasible in certain situations. We will briefly look at two examples, side by side, of how we can convert a conventional Java snippet into a Lambda expression.

In the following code, we will assign a method to a variable called blockofCodeA. This is just what we are intending to solve with the means of Lambda expressions:

blockofCodeA = public void demo(){ System.out.println("Hello World");
}

The same piece of code can be written using Lambda expressions, as shown here:

blockofCodeA = () -> {                                 
    System.out.println("Hello World");
}

Remove the name, return type, and the modifier, and simply add the arrow after the brackets. This becomes your Lambda expression.