Lambda Expressions

Lambda expressions enable functional programming in Java by allowing the creation of anonymous functions ( like we see in inner classes, annoymous inner class ). They provide a concise syntax for writing code that takes advantage of functional interfaces (interfaces with a single abstract method) and enables functional programming paradigms such as map, filter, and reduce operations.

Lambda expression is a shorthand way of writing an instance of a class that implements a functional interface.

Where to Use:

Replacing anonymous classes in event handling
Functional programming with the Stream API
Reducing boilerplate code

Code Example

​x
 
interface DogCourier{    public boolean test(Dog d);}​class Dog{    int age;        public Dog(int age)    {    this.age = age;    }        public int getAge()    {    return age;    }}​public class Test{    public static void main(String[] args)    {           Dog d = new Dog(10);                /* old way of implement the interface method using Anonymous inner class        DogCourier d = new DogCourier() {            public boolean test(Dog d1) {                return d1.getAge() > 9;            }        };        */        DogCourier dc = dog -> {            return dog.getAge() > 10;        };​        // DogCourier d = (Dog newDC) -> return newDC.getAge() > 9; // compiler error        boolean result = dc.test(d);        System.out.println(result);    }}

Output

false

1: EvenOdd

2: Add Two Numbers

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import java.util.*;​interface EvenOdd{    public boolean isEven(int a);}​public class EvenOddTest{    public static void main(String[] args)    {        /*        EvenOdd result = (a) -> {           return a % 2 == 0;        };        */​        // (OR)        // lambda expressions returns the results automatically        EvenOdd result = a -> a % 2 == 0;         System.out.println(result.isEven(30));        System.out.println(result.isEven(11));    }}

Output

true
false

Lambda Expressions

Output

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