Apprendre Introduction to Lambda Expressions | Getting Started with Lambda Expressions

Lambda expressions are a key feature introduced in Java to enable you to write code that is more concise, readable, and expressive, especially when dealing with functional-style operations. Before lambda expressions, you often had to use anonymous inner classes to provide the implementation for interfaces with a single abstract method, such as Runnable or Comparator. This led to verbose and cluttered code, making it harder to focus on the business logic. Lambda expressions address this challenge by allowing you to write the same logic in a much simpler and more direct way, reducing boilerplate and improving clarity.

Main.java


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package com.example;

import java.util.Arrays;
import java.util.Comparator;

public class Main {
    public static void main(String[] args) {
        // Using an anonymous inner class to implement Runnable
        Runnable runnableOld = new Runnable() {
            @Override
            public void run() {
                System.out.println("Hello from anonymous inner class!");
            }
        };
        runnableOld.run();

        // Using a lambda expression to implement Runnable
        Runnable runnableLambda = () -> System.out.println("Hello from lambda expression!");
        runnableLambda.run();
    }
}

The syntax of a lambda expression in Java consists of three main parts: the parameter list, the arrow token (->), and the body. The parameter list defines the inputs to the lambda, and it can be empty, a single parameter, or multiple parameters enclosed in parentheses. The arrow token separates the parameters from the body. The body can be a single expression or a block of code enclosed in curly braces. For example, in the lambda expression (a, b) -> a + b, (a, b) is the parameter list, -> is the arrow token, and a + b is the body.

Main.java


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package com.example;

import java.util.Arrays;
import java.util.Comparator;

public class Main {
    public static void main(String[] args) {
        Integer[] numbers = {5, 2, 9, 1, 3};

        // Comparator using a lambda expression with multiple parameters and a single statement body
        Comparator<Integer> comparator = (a, b) -> a - b;
        Arrays.sort(numbers, comparator);

        System.out.println("Sorted numbers:");
        for (int n : numbers) {
            System.out.print(n + " ");
        }
    }
}

1. Which part of a lambda expression specifies its input values?

2. What is the main advantage of using lambda expressions over anonymous inner classes in Java?

3. What is the return type of this lambda expression if `a` and `b` are both declared as `int` in the context where the lambda is used?

Tout était clair ?

Merci pour vos commentaires !

Section 1. Chapitre 1

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Suggested prompts:

Can you give me more examples of lambda expressions in Java?

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Main.java


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package com.example;

import java.util.Arrays;
import java.util.Comparator;

public class Main {
    public static void main(String[] args) {
        // Using an anonymous inner class to implement Runnable
        Runnable runnableOld = new Runnable() {
            @Override
            public void run() {
                System.out.println("Hello from anonymous inner class!");
            }
        };
        runnableOld.run();

        // Using a lambda expression to implement Runnable
        Runnable runnableLambda = () -> System.out.println("Hello from lambda expression!");
        runnableLambda.run();
    }
}

Main.java


              1234567891011121314151617181920
            
package com.example;

import java.util.Arrays;
import java.util.Comparator;

public class Main {
    public static void main(String[] args) {
        Integer[] numbers = {5, 2, 9, 1, 3};

        // Comparator using a lambda expression with multiple parameters and a single statement body
        Comparator<Integer> comparator = (a, b) -> a - b;
        Arrays.sort(numbers, comparator);

        System.out.println("Sorted numbers:");
        for (int n : numbers) {
            System.out.print(n + " ");
        }
    }
}

1. Which part of a lambda expression specifies its input values?

2. What is the main advantage of using lambda expressions over anonymous inner classes in Java?

3. What is the return type of this lambda expression if `a` and `b` are both declared as `int` in the context where the lambda is used?

Tout était clair ?

Merci pour vos commentaires !

Section 1. Chapitre 1

Introduction to Lambda Expressions

1. Which part of a lambda expression specifies its input values?

2. What is the main advantage of using lambda expressions over anonymous inner classes in Java?

3. What is the return type of this lambda expression if a and b are both declared as int in the context where the lambda is used?

Introduction to Lambda Expressions

1. Which part of a lambda expression specifies its input values?

2. What is the main advantage of using lambda expressions over anonymous inner classes in Java?

3. What is the return type of this lambda expression if a and b are both declared as int in the context where the lambda is used?

3. What is the return type of this lambda expression if `a` and `b` are both declared as `int` in the context where the lambda is used?

3. What is the return type of this lambda expression if `a` and `b` are both declared as `int` in the context where the lambda is used?