Java Articles - Page 140 of 440

A PropertyChangeListener is a functional interface from java.beans package. It has one abstract method propertyChange() and gets called when a bound property is changed. This method takes a PropertyChangeEvent argument that has details about an event source and the property that has changed. A PropertyChangeSupport can be used by beans that support bound properties. It can manage a list of listeners and dispatches property change events. The PropertyChangeListener's implementer does the role of an Observer and bean wrapping the PropertyChangeSupport is Observable.Syntaxvoid propertyChange(PropertyChangeEvent evt)Exampleimport java.beans.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.border.*; public class PropertyChangeListenerLambdaTest {    public static void main(String [] args) {   ... Read More

Lambda expression is the anonymous representation of a function descriptor of a functional interface. As we know that all collection interfaces like List, Set and Queue use an Iterable as their super interface. Since Java 8, an Iterable interface introduces a new method called forEach(). This method performs an action on the contents of Iterable in the order elements that occur when iterating until all elements have processed.Syntaxvoid forEach(Consumer

BinaryOperator is one of a functional interface from java.util.function package and having exactly one abstract method. A lambda expression or method reference uses BinaryOperator objects as their target. BinaryOperator interface represents a function that takes one argument of type T and returns a value of the same type.BinaryOperator Interface contains two static methods, minBy() and maxBy(). The minBy() method returns a BinaryOperator that returns the greater of two elements according to a specified Comparator while the maxBy() method returns a BinaryOperator that returns the lesser of two elements according to a specified Comparator.Syntax@FunctionalInterface public interface BinaryOperator extends BiFunctionExampleimport java.util.function.BinaryOperator; public class BinaryOperatorTest {    public static void main(String[] args) {       BinaryOperator ... Read More

In this problem we are given an array of numbers, and we have to find the largest, smallest, second largest, and second smallest elements in an array in Java. Let’s understand the problem better with the help of an example: Input int arr[] = {55, 10, 8, 90, 43, 87, 95, 25, 50, 12}; Output Smallest element = 8 2nd Smallest element = 10 Largest element = 95 2nd Largest element = 90 To solve this problem, use the following approaches: Using Arrays.sort() Using nested for-loops Optimized one-pass approach Using Arrays.sort() In this ... Read More

Given a list of numbers, our task is to calculate the average of this list. The average of a list can be found by adding all the elements in the list and dividing the sum by the total number of elements. In this article we will learn different methods to implement this in Java. There are multiple ways in Java to find the average of a list. In this article we will explore two different approaches: Using Java Streams Using for loop Find Average of a List Using Java Streams This approach shows how to find ... Read More

A Supplier interface is a pre-defined interface that represents the supplier of results. It is instantiated using lambda expression or method reference or default constructor. The functional method of a Supplier interface is the get() method. This interface belongs to java.util.function package.Syntax@FunctionalInterface public interface SupplierIn the below program, we can use the Supplier interface in a lambda expression. The get() method only returns a value and doesn't accept any argument, so a lambda expression having an empty argument part.Exampleimport java.util.*; import java.util.function.*; public class SupplierTest {    public static void main(String args[]) {       Supplier supplier1 = () -> "TutorialsPoint";   // lambda expression       System.out.println(supplier1.get());       ... Read More

A Predicate interface defined in java.util.function package. It represents a boolean-valued function with one argument. It is kind of a functional interface whose functional method is the test(). BiPredicate interface is similar to the Predicate interface with two arguments. It can be used as an assignment target for a lambda expression.Syntax for Predicate@FunctionalInterface public interface PredicateExampleimport java.util.*; import java.util.function.*; import java.util.stream.*; public class EmployeePredicateTest {    public static void main(String[] args) {       Employee e1 = new Employee(1, 23, "M", "Raja");       Employee e2 = new Employee(2, 13, "M", "Jai");       Employee e3 = new Employee(3, 36, "F", "Yamini");       ... Read More

Comparator interface can be used to order the objects of user-defined classes. It is capable of comparing two objects of two different classes. We can sort a list of objects where we can't modify the object’s source code to implement Comparable interface. A lambda expression can't be executed on its own and used to implement methods that are declared in a functional interface.In the below example, we need to sort a list by name using the Comparator interface and Stream API with the help of lambda expressions.Exampleimport java.util.*; import java.util.function.*; import java.util.stream.*; public class ListSortByNameTest {    public static void main(String[] args) {       List arrayList = new ArrayList(); ... Read More

The Function interface is a pre-defined functional interface that can be used as an assignment target for a lambda expression or method reference. It takes a single parameter and returns result by calling the apply() method. While the BiFunction interface is also a pre-defined functional interface that takes two parameters and returns a result. It is similar to the Function interface except it takes two parameters.Syntax@FunctionalInterface public interface Function @FunctionalInterface public interface BiFunctionExampleimport java.util.function.BiFunction; import java.util.function.Function; public class SampleFunctionBiFunctionTest {    public static void main(String[] args) {       Function printNumber = a -> a*10;       System.out.println("The number is: "+ printNumber.apply(10));   ... Read More

A Consumer interface is a predefined functional interface that can be used when creating lambda expressions or method references. This interface represents an operation that accepts a single input parameter and doesn't return anything. It contains only one method named accept(). The BiConsumer interface is similar to a Consumer interface and accepts two input parameters and doesn’t return anything.Syntax@FunctionalInterface public interface Consumer @FunctionalInterface public interface BiConsumerExampleimport java.util.*; import java.util.function.*; public class ConsumerBiConsumerTest {    public static void main(String[] args) {       Consumer c = (x) -> System.out.println(x.toLowerCase());  // lambda expression       c.accept("Raja");         Consumer con = (x) -> {  // ... Read More