Java Lambda Expressions

Lambda Expressions are the most remarkable feature added to the Java platform with Java 8. It’s specified in JSR 335 and JEP 126. The very need for this feature is to gain some of the capabilities supplied by functional programming. The main idea behind this concept is to be able to parametrize the functions for subsequent executions of them.

Till Java 8, this could already be simulated via the use of anonymous inner classes with some design patterns like command pattern and functors. However, the adoption of lambda expressions gave way to the direct use of this concept.

1. What is a Lambda Expression?

A lambda expression is a piece of code that is giving an alternative way to the anonymous class to pass the function as a parameter to other subsequent flows of code such as methods, constructors, etc… In this approach, a function can be referenced with a variable and passed as a reference to be executed in a subsequent flow of code execution.

The structure of a lambda expression is as follows; it is formed of some arguments, followed by an arrow and that’s followed by a code block.

Lambda Expression

Lambda Expression

2. Type of Lambda Expressions; Functional Interfaces

A lambda expression is identified by a special single-method interface called Functional Interface. A functional interface is the target type that’s determined by the compiler and used as the type of the reference to the lambda expression.

This binding of a lambda expression to a functional interface is determined from the context of the lambda expression. That means, the binding of a lambda expression to a target type can take place in different contexts such as variable declarations, method arguments, constructors, etc.; and from this binding, the compiler finds the target type, which is a functional interface, and infers the types of the parameters used in the lambda expression according to that functional interface.

A functional interface can be marked with an informative annotation @FunctionalInterface that can be used to inform other developers.

Let’s do a simple example to understand it well.

Think that we want to lowercase or uppercase a text based on a condition.

It will be a dynamic evaluation so we can abstract the operation.

By leveraging the lambda expressions we can do it as following:

Here is the lambda expressions for case operations:

t -> t.toUpperCase();
t -> t.toLowerCase();

By looking at the code above, we see that there is a parameter t; we do not know its type, and in the code block of the expression, the methods of t, which are toUpperCase and toLowerCase, are called.

To be able to pass these expressions to somewhere, we have to declare a functional interface; with that single-method interface, the compiler will be able to infer the type of t:

public interface CaseOperation {
    String operate(String text);

Then we can write our main code as such:

public void printWithCaseOperation(String text, CaseOperation operation){


public void mainCode(){

        printWithCaseOperation("Hello Lambda!", t -> t.toUpperCase());
    } else {
        printWithCaseOperation("Hello Lambda!", t -> t.toLowerCase());

Here, when we call the method printWithCaseOperation with a lambda expression as its second parameter, the compiler infers that the method’s second parameter is of type CaseOperation and, so is also of the lambda expression’s type, too.

3. Some Internals

At this point, let’s watch this video to listen to the internals of lambda expressions.

For whom needs some speed, I will summarize it, you’re welcome:

  • We need lambdas basically since of; parallel friendly APIs and less code with the usage of closure-like functional programming capabilities.
  • Lambdas are not a new function type in the VM-level; it’s mostly about compiler level.
  • The compiler does a great job for us by transforming our lambdas into the form of a related defined functional interface. In other words; the compiler infers our lambdas as functional interfaces.
  • When the compiler sees the lambda expression, it simply creates a static method from the resolved related functional interface and in the invocation time, the VM executes that method by calling invokedynamic which is an invocation mode introduced in Java SE 7.

4. Lambda Syntax

Java Lambda Expressions have a basic structure as drawn in the diagram above. Besides this, some inferences can be made automatically by the compiler for us. When writing lambda expressions these compiler inferences directs us to write less code.

#java #programming #developer

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Java Lambda Expressions
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Tyrique Littel


How to Install OpenJDK 11 on CentOS 8

What is OpenJDK?

OpenJDk or Open Java Development Kit is a free, open-source framework of the Java Platform, Standard Edition (or Java SE). It contains the virtual machine, the Java Class Library, and the Java compiler. The difference between the Oracle OpenJDK and Oracle JDK is that OpenJDK is a source code reference point for the open-source model. Simultaneously, the Oracle JDK is a continuation or advanced model of the OpenJDK, which is not open source and requires a license to use.

In this article, we will be installing OpenJDK on Centos 8.

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Lambda Expression in Java 8

In this blog we will understand what is the lambda expression and why we need lambda expression and how we use lambda and about the functional interface.

What is Lambda Expression :
  • It is an anonymous function.
  • Not having name
  • No return type and no modifiers.

#functional programming #java #functional java #java #java 8 #java8 #lambda expressions in java

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According to some surveys, such as JetBrains’s great survey, Java 8 is currently the most used version of Java, despite being a 2014 release.

What you are reading is one in a series of articles titled ‘Going beyond Java 8,’ inspired by the contents of my book, Java for Aliens. These articles will guide you step-by-step through the most important features introduced to the language, starting from version 9. The aim is to make you aware of how important it is to move forward from Java 8, explaining the enormous advantages that the latest versions of the language offer.

In this article, we will talk about the most important new feature introduced with Java 10. Officially called local variable type inference, this feature is better known as the **introduction of the word **var. Despite the complicated name, it is actually quite a simple feature to use. However, some observations need to be made before we can see the impact that the introduction of the word var has on other pre-existing characteristics.

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Java Lambda Expressions Example | Lambda Expression in Java

Java lambda expressions are unnamed methods, which are used to implement the abstract method of functional interface. Lambda expressions are also known as closures. They are used to call methods as  objects.

The lambda expressions are added in Java 8 and provide below functionalities.

  1. It enables to treat functionality as the method argument, or code as data.
  2. The function that can be created without belonging to any class.
  3. The lambda expression can be passed around as if it was an object and executed on demand.

Java Lambda Expressions

Lambda expressions use the lambda operator (->) which divides the lambda expression into two parts. The part on the left side contains the parameters required by the lambda expression, and the part on the right side specifies the body of the lambda expression.

The parameters are enclosed in parenthesis, and the body is enclosed in curly braces.

Note: A functional interface is an  interface that contains only one abstract method. A functional interface is also known as SAM(Single Abstract Method) interface. @FunctionalInterface could be written to create a functional interface that will show an error if the properties of the functional interface got violated.

#java #lambda expressions #java 8

Tyrique  Littel

Tyrique Littel


Lambda Expressions: An Introduction in Java 8

Lambda expressions were one of the new features that was introduced in Java 8.

They help clean up verbose code by providing a concise and local way to reduce redundancy by keeping code short and self-explanatory.

In addition to saving code, Java’s lambda expressions are important in functional programming. They allow developers to write in a functional style by acting as functions without belonging to any class.

Lambda expressions allow us to implement functional interfaces by converting them into instances of functional interfaces. This provides a reference to the function. For example, a lambda passed as a parameter is indistinguishable to calling an implemented interface method). Thus, the references are used effectively as a function type object that can be passed and called on.

#java #tech blogs #java 8 #lambda expressions in java