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Articles by raja
Page 10 of 38
How to use FileFilter interface in lambda expression in Java?
A FileFilter is a functional interface from the "java.io" package. It can be used as the assignment target for a lambda expression or method reference. An instance of the FileFilter interface passed to the listFiles() method of the File class. FileFilter interface having one abstract method accept() and it tests whether or not the specified abstract pathname has included in a pathname list.Syntax@FunctionalInterface public interface FileFilterExampleimport java.io.File; import java.io.FileFilter; public class FileFilterTest { public static void main(String[] args) { File dir = new File("C:/Program Files/Java/jdk1.8.0_211"); ...
Read MoreHow to implement PropertyChangeListener using lambda expression in Java?
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 MoreHow to iterate the contents of a collection using forEach() in Java?
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
Read MoreHow to use BinaryOperator interface in lambda expression in Java?
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; ...
Read MoreHow to use Supplier interface in lambda expression in Java?
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[]) { ...
Read MoreHow to use Predicate and BiPredicate in lambda expression in Java?
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, ...
Read MoreHow to sort a list by name using a Comparator interface in Java?
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 MoreHow to use Function and BiFunction interfaces in lambda expression in Java?
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 = ...
Read MoreHow to use Consumer and BiConsumer interfaces in lambda expression in Java?
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 ...
Read MoreHow can we write Callable as a lambda expression in Java?
A Callable interface defined in java.util.concurrent package. An object of Callable returns a computed result done by a thread in contrast to a Runnable interface that can only run the thread. The Callable object returns Future object that provides methods to monitor the progress of a task executed by a thread. An object of the Future used to check the status of a Callable interface and retrieves the result from Callable once the thread has done.In the below example, we can write a Callable interface as a Lambda Expression.Exampleimport java.util.concurrent.*; public class LambdaCallableTest { public static ...
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