An interface defined with only one abstract method is known as Functional Interface. It's not mandatory to mark the functional interface with @FunctionalInterface annotation, the compiler doesn't throw any error. But it’s good practice to use @FunctionalInterface annotation to avoid the addition of extra methods accidentally. If an interface annotated with @FunctionalInterface annotation and more than one abstract method then it throws a compile-time error.Syntax@FunctionalInterface interface interface_name {    // only one abstarct method declaration }Example@FunctionalInterface interface Shape {    void printArea(int x); } public class SquareTest {    public static void main (String args[]) {       Shape square ... Read More

The lambda expression composed of two parts, one is an argument and another one is code or expression. These two parts have separated by an arrow operator "->". We can use different IDE's like Netbeans, IntelliJ,  and Eclipse to debug the lambda expressions in Java. It is always possible to create multi-line lambda expressions and use print statements to display the values of a variable. The debugger can also provide additional information about the state of a java program. It allows some variables to be modified while the debugger is executing.Syntax(parameters) -> expression   or (parameters) -> { statements; }Exampleimport java.util.*; public class LambdaDebugTest { ... Read More

Lambda expression is an anonymous method that has used to provide an implementation of a method defined by a functional interface. In Java 8, it is also possible for the body of a lambda expression to be a complex expression or statement, which means a lambda expression consisting of more than one line. In that case, the semicolons are necessary. If the lambda expression returns a result then the return keyword is also required.Syntax([comma seperated argument-list]) -> { multiline statements }Exampleinterface Employee {    String displayName(String s); } public class MultilineLambdaTest {    public static void main(String[] s) {       ... Read More

The java.util.function package defines several in-built functional interfaces that can be used when creating lambda expressions or method references.Inbuilt functional interfaces:1) Function InterfaceThe Function interface has only one single method apply(). It can accept an object of any data type and returns a result of any datatype.Exampleimport java.util.*; import java.util.function.*; public class FunctionTest {    public static void main(String args[]) {       String[] countries = {"India", "Australia", "England", "South Africa", "Srilanka", "Newzealand", "West Indies", "Scotland"};       Function converter = (all) -> {  // lambda expression          String names = "";       ... Read More

A constructor reference is just like a method reference except that the name of the method is "new". It can be created by using the "class name" and the keyword "new" with the following syntax.Syntax :: newIn the below example, we are using java.util.function.Function. It is a functional interface whose single abstract method is the apply(). The Function interface represents an operation that takes single argument T and returns a result R.Exampleimport java.util.function.*; @FunctionalInterface interface MyFunctionalInterface {    Employee getEmployee(String name); } class Employee {    private String name;    public Employee(String name) {       this.name = name;    }    public String ... Read More

When we are using a lambda expression for java listener, we do not have to explicitly implement the ActionListener interface. Instead, we can use the below syntax.Syntaxbutton.addActionListener(e -> { // some statements });An ActionListener interface defines only one method actionPerformed(). It is a functional interface which means that there's a place to use lambda expressions to replace the code.Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; public class LambdaListenerTest extends JFrame {    public static void main(String args[]) {       new LambdaListenerTest();    }    private JButton button;    public ClickMeLambdaTest() {       setTitle("Lambda Expression Test");       button = ... Read More

A lambda expression passed in a method that has an argument of type of functional interface. If we need to pass a lambda expression as an argument, the type of parameter receiving the lambda expression argument must be of a functional interface type.In the below example, the lambda expression can be passed in a method which argument's type is "TestInterface". Exampleinterface TestInterface {    boolean test(int a); } class Test {    // lambda expression can be passed as first argument in the check() method    static boolean check(TestInterface ti, int b) {       return ti.test(b);    } } public class ... Read More

The lambda expressions consist of two parts, one is parameter and another is an expression and these two parts have separated by an arrow (->) symbol. A lambda expression can access a variable of it's enclosing scope. A Lambda expression has access to both instance and static variables of it's enclosing class and also it can access local variables which are effectively final or final.Syntax( argument-list ) -> expressionExampleinterface TestInterface {    void print(); } public class LambdaExpressionTest {    int a; // instance variable    static int b; // static variable    LambdaExpressionTest(int x) {    // constructor to initialise instance variable       this.a = ... Read More

This Question comes to many professionals who are not actually into core technical and want to pursue their career in Selenium Automation. The term coding makes the non-programmers a bit scare to even start off with something like automation. There is a perception that a non-programmer cannot excel in Automation, but it is only in head. Many deserving and capable manual testers shy away from Selenium just thinking that it require some special skills.There are various many languages in which Selenium Scripts are designed such as Python, Ruby, C#, JavaScript and Java is one such of them. Knowing the popularity ... Read More

Java supports lambda expressions but not the Closures. A lambda expression is an anonymous function and can be defined as a parameter. The Closures are like code fragments or code blocks that can be used without being a method or a class. It means that Closures can access variables not defined in its parameter list and also assign it to a variable.Syntax([comma seperated parameter-list]) -> {body}In the below example, the create() method has a local variable "value" with a short life and disappears when we exit the create() method. This method returns the closure to the caller in the main() method after that ... Read More