ToDoubleFunction is a functional interface defined in java.util.function package. This functional interface expects a parameter as input and produces a double-valued result. It is used as an assignment target for a lambda expression or method reference. ToDoubleFunction interface contains only one abstract method, applyAsDouble().Syntax@FunctionalInterface public interface ToDoubleFunction {    double applyAsDouble(T value); }Example-1import java.util.function.ToDoubleFunction; ... Read More

The Runnable interface is a functional interface defined in java.lang package. This interface contains a single abstract method, run() with no arguments. When an object of a class implementing this interface used to create a thread, then run() method has invoked in a thread that executes separately.Syntax@FunctionalInterface public interface Runnable {  void run(); ... Read More

JavaFX Button class provides the setOnAction() method that can be used to set an action for the button click event. An EventHandler is a functional interface and holds only one method is the handle() method.Syntax@FunctionalInterface public interface EventHandler extends EventListenerIn the below example, we can able to implement event handling of JavaFX ... Read More

The DoubleFunction is a built-in functional interface defined in java.util.function package. This interface accepts one double-valued parameter as input and returns a value of type R. As this is a functional interface, it can be used as an assignment target for a lambda expression or method reference. DoubleFunction interface having only one abstract method, ... Read More

A prime number is a number that is greater than 1 and divided by 1 or itself only. It other words, it can't be divided by other numbers than itself or 1. The generation of prime numbers is 2, 3, 5, 7, 11, 13, 17 and etc.In the below example, we can generate the prime numbers with the ... Read More

IntFunction interface is a functional interface in Java 8 and defined in java.util.function package. This interface accepts an int-valued parameter as input and returns a value of type R. IntFunction interface can be used as an assignment target for a lambda expression or method reference and holds only one abstract method, apply().Syntax@FunctionalInterface public interface IntFunction {    R ... Read More

The Fibonacci is a sequence of numbers in which every number after the first two numbers is the sum of the two preceding numbers like 0, 1, 1, 2, 3, 5, 8, 13, 21 and so on. The sequence of Fibonacci numbers defined by using "F(n)=F(n-1)+F(n-2)".In the below example, we can implement ... Read More

Java 8 introduced changes in the Comparator interface that allows us to compare two objects. These changes help us to create comparators more easily. The first important method added is the comparing() method. This method receives as a parameter Function that determines the value to be compared and creates Comparator. Another important ... Read More

A Map is a collection object that maps keys to values in Java. The data can be stored in key/value pairs and each key is unique. These key/value pairs are also called map entries.In the below example, we can populate a Map using a lambda expression. We have passed Character and Runnable arguments to Map object and ... Read More

The ObjIntConsumer interface is a kind of functional interface and defined in java.util.function package. This functional interface expects an object-valued and int-valued argument as input and does not produce any output. It holds only one functional method, accept(Object, int).Syntax@FunctionalInterface    public interface ObjIntConsumer {       void accept(T t, int value) }In the ... Read More