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Java Articles
Page 285 of 450
How 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 ...
Read MoreWhat are the SAM Interfaces in Java?
An interface having only one abstract method is known as a functional interface and also named as Single Abstract Method Interfaces (SAM Interfaces). One abstract method means that either a default method or an abstract method whose implementation is available by default is allowed. The instances of SAM interfaces are java.lang.Runnable, java.awt.event.ActionListener, java.util.Comparator and java.util.concurrent.Callable. The SAM interfaces can be implemented using lambda expressions or method references.Syntax@FunctionalInterface public interface Changeable { public void change(T o); }Example@FunctionalInterface interface MyInterface { String reverse(String n); } public class LambdaReverseTest { public static void main( String[] args ...
Read MoreWhat are the rules for formal parameters in a lambda expression in Java?
A lambda expression is similar to a method that has an argument, body, and return type. It can also be called an anonymous function (method without a name). We need to follow some rules while using formal parameters in a lambda expression.If the abstract method of functional interface is a zero-argument method, then the left-hand side of the arrow (->) must use empty parentheses.If the abstract method of functional interface is a one-argument method, then the parentheses are not mandatory.If the abstract method of functional interface is a multiple argument method, then the parentheses are mandatory. The formal parameters are comma-separated and can be in the same order of the ...
Read MoreWhat are the rules for the body of lambda expression in Java?
A lambda expression is an anonymous function (nameless function) that has passed as an argument to another function. We need to follow some rules while using the body of a lambda expression.Rules for the body of a lambda expressionThe body of the lambda expression can be either a single expression or more statements.If we are using a single expression as the body of a lambda expression, then no need to enclose the body with curly braces ({}).If we are using one or more statements as the body of a lambda expression, then enclosing them within curly braces({}) can be mandatory.Syntax(parameters) ...
Read MoreHow to sort a collection by using Stream API with lambdas in Java?
A Stream API is a powerful way to achieve functional programming in Java. It usually works in conjunction with a lambda expression and provides an efficient way to perform data manipulation operations like sort, filter, map, reduce and etc.In the below example, we can sort a collection using Stream API. It provides sorting logic by using the sorted() method of the Comparator interface. If we have two Comparator interface instances and need to do sorting by composite condition (by the first comparator and then by the second comparator), we can use both comparators by invoking the thenComparing() method on the ...
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