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Programming Articles
Page 2306 of 2547
How 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 MoreHow to write text and output it as a text file using R?
The easiest way to write text and obtain it as an output is done by using writeLines function and cat function, and the output of these functions are connected with the help fileConn and sink.Example> fileConn writeLines(c("TutorialsPoint", "SIMPLY EASY LEARNING"), fileConn) > close(fileConn)We can do the same and view these files in R as follows −> fileConn writeLines(c(paste("TutorialsPoint", "E-learning"), "2006", "Video Courses", "Tutorials", "Books"), fileConn) > close(fileConn) > file.show("example.txt")Using sink function> sink("example3.txt") > cat("TutorialsPoint", "E-learning") > cat("") > cat("2006") > cat("") > cat("Video Courses") > cat("") > cat("Tutorials") > cat("") > cat("Books") > sink()Using only cat function> cat("TutorialsPoint E-learning", ...
Read MoreWhat is the use of tilde operator (~) in R?
Tilde operator is used to define the relationship between dependent variable and independent variables in a statistical model formula. The variable on the left-hand side of tilde operator is the dependent variable and the variable(s) on the right-hand side of tilde operator is/are called the independent variable(s). So, tilde operator helps to define that dependent variable depends on the independent variable(s) that are on the right-hand side of tilde operator.Example> Regression_Model Regression_Data Regression_Model_New < - lm(y~ . , data = Regression_Data)This will have the same output as the previous model, but we cannot use tilde with dot if ...
Read MoreHow to simulate discrete uniform random variable in R?
There is no function in base R to simulate discrete uniform random variable like we have for other random variables such as Normal, Poisson, Exponential etc. but we can simulate it using rdunif function of purrr package.The rdunif function has the following syntax −> rdunif(n, b , a)Here, n = Number of random values to returnb = Maximum value of the distribution, it needs to be an integer because the distribution is discretea = Minimum value of the distribution, it needs to be an integer because the distribution is discreteExampleLet’s say you want to simulate 10 ages between 21 to ...
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 ...
Read MoreImportance of Predicate interface in lambda expression in Java?
Predicate is a generic functional interface that represents a single argument function that returns a boolean value (true or false). This interface available in java.util.function package and contains a test(T t) method that evaluates the predicate of a given argument.Syntaxpublic interface Predicate { boolean test(T t); }Exampleimport java.util.*; import java.util.functionPredicate; public class LambdaPredicateTest { public static void main(String args[]) { Employee emp1 = new Employee("Raja", 26); Employee emp2 = new Employee("Jaidev", 24); Employee emp3 = new Employee("Adithya", ...
Read MoreHow to use method references with Generics in Java?
The method references are introduced in Java 8 similar to lambda expression. It can allow us to reference methods or constructors without executing them. The method references and lambda expressions require a target type that consists of a compatible functional interface. We can also use a method reference with generic classes and generic methods in java.Exampleinterface MyFunc { int func(T[] vals, T v); } class MyArrayOps { static int countMatching(T[] vals, T v) { int count = 0; for(int i=0; i < ...
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