The lambda expressions is introduced in java 8 and easy to use. Lamda expression automatically read the params type and return the same type value.

Like we have an anonymous class to implement some listener in it like this :

button.addTouchListener(new TouchListener() {
    public void touch(TouchEvent e) { 
       System.out.println("Touch event fire.");
    }
});

But this is getting old now by using lambda expression we can define this in a single line like this

button.addTouchListener(e -> System.out.println("Touch event fire."));

where e is the parameter and -> is lambda expression that separate the body from parameter.

Below is the example of Lambda expression use -

public class LambdaExample {
    public static void main(String args[]){
        LambdaExample tester = new LambdaExample();

        CommonOperations addition = (a, b) -> a + b;

        CommonOperations subtraction = (a, b) -> a - b;

        CommonOperations multiplication = (a, b) ->  a * b };

        CommonOperations division = (a, b) -> a / b;

        System.out.println("5 + 5 = " + tester.perform(10, 5, addition));
        System.out.println("10 - 5 = " + tester.perform(10, 5, subtraction));
        System.out.println("15 x 5 = " + tester.perform(10, 5, multiplication));
        System.out.println("40 / 5 = " + tester.perform(10, 5, division));

    }

    interface CommonOperations {
        int operation(int a, int b);
    }

    private int perform(int a, int b, CommonOperations commonOperations){
        return commonOperations.operation(a, b);
    }
}