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Java Lambda Expressions

Lambda expressions are introduced in java8, It offer a way to create anonymous functions. Essentially, they allow functions to be treated as if they were regular variables in Java. This implies that it can be used as variables, returned as values from other functions, and passed as arguments to other functions.

A function that doesn't need to be part of any specific class; without belonging to any class

With Lambda Expressions, you can pass around these functions as if they were regular objects, and they can be executed whenever needed.

Table Of Content

Java Lambda Expressions
Types of Lambda expressions
Problem Without Lambda Expression
Java Lambda expressions without parameter
Java Lambda expressions of Foreach Loop

Lambda expressions

(parameters) -> expression

or,

(parameters) -> { statements }

The first form is called the "expression lambda," and the second form is called the "block lambda." In both cases, the "parameters" represent the arguments to the lambda expression, and the "- >" this operator separates the body of the lambda expression from parameters.

Example of an expression lambda

// Create a lambda expression that returns the square of a number
Function<Integer, Integer> square = (x) -> Y * Y;

In this example, the "Function" interface is used to represent a function that takes an integer as input and returns an integer as output. The lambda expression "(x) -> x * x" is assigned to the "square" variable, which can then be used like any other function.

Example of an block lambda

// Create a lambda expression that prints the elements of an array
Consumer<String[]> printArray = (arr) -> {
    for (String element : arr) {
        System.out.println(element);
    }
};

In this example, the "Consumer" interface is used to represent a function that takes an array of strings as input and returns no output. The lambda expression "(arr) -> { for (String element : arr) { System.out.println(element); } }" is assigned to the "printArray" variable.

Example : Without Lambda Expression

import java.util.Scanner;

public class AverageCalculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("How many numbers do you want to enter? ");
        int count = scanner.nextInt();

        int sum = 0;
        for (int i = 0; i < count; i++) {
            System.out.print("Enter number #" + (i + 1) + ": ");
            int number = scanner.nextInt();
            sum += number;
        }

        double average = (double) sum / count;
        System.out.println("The average of the numbers is: " + average);
    }
}

Output:

How many numbers do you want to enter? 5
Enter number #1: 10
Enter number #2: 20
Enter number #3: 30
Enter number #4: 40
Enter number #5: 50
The average of the numbers is: 30.0

Lambda expressions

A concise way of expressing a single method interface using an expression. This is helpful in writing functional programming style code.

Java example of Lambda expressions

 // Java example of Lambda expressions

import java.util.Scanner;
import java.util.stream.IntStream;

public class AverageCalculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("How many numbers do you want to enter? ");
        int count = scanner.nextInt();

        System.out.print("Enter the numbers separated by spaces: ");
        int[] numbers = IntStream.range(0, count)
                                 .map(i -> scanner.nextInt())
                                 .toArray();

        double average = IntStream.of(numbers)
                                  .average()
                                  .orElse(Double.NaN);

        System.out.println("The average of the numbers is: " + average);
    }
}

Output:

How many numbers do you want to enter? 5
Enter the numbers separated by spaces: 10 20 30 40 50
The average of the numbers is: 30.0