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Articles by raja
Page 31 of 38
How to print different stack frames using StackWalker API in Java?
Java 9 defines a StackWalker API that provides laziness and frame filtering. An object of StackWalker allows us to traverse and access stacks and contains one useful method: walk(). This method opens a StackFrame stream for the current thread, then applies the function with that StackFrame stream. We need to get StackWalker object, then use StackWalker.getInstance() method.In the below example, we can print different stack frames: all stack frames, skip some stack frames and limit stack frames by using StackWalker API.Exampleimport java.lang.StackWalker.StackFrame; import java.util.*; import java.util.stream.*; public class StackWalkerTest { public static void main(String args[]) { ...
Read MoreHow can we implement the SubmissionPublisher class in Java 9?
Since Java 9, we can create Reactive Streams by introducing four core interfaces: Publisher, Subscriber, Subscription, Processor, and one concrete class: SubmissionPublisher that implements the Publisher interface. Each interface plays a different role, corresponding to the principles of Reactive Streams. We can use the submit() method of SubmissionPublisher class to publish the provided item to each subscriber.Syntaxpublic class SubmissionPublisher extends Object implements Flow.Publisher, AutoCloseableIn the below example, we can implement the SubmissionPublisher classExampleimport java.util.concurrent.Flow.Subscriber; import java.util.concurrent.Flow.Subscription; import java.util.concurrent.SubmissionPublisher; class MySubscriber implements Subscriber { private Subscription subscription; private String name; public ...
Read MoreWhat are the core interfaces of Reactive Streams in Java 9?
Java 9 has introduced Reactive Streams under java.util.concurrent.Flow package that supports an interoperable publish-subscribe framework. It processes an asynchronous stream of data across the asynchronous boundary (passing elements into another thread or thread-pool), and the receiving side is not forced to buffer arbitrary amounts of data, then buffer overflow can't occur.Flow API contains four interrelated core interfaces: Publisher, Subscriber, Subscription, and Processor.Syntax@FunctionalInterface public static interface Publisher { public void subscribe(Subscriber
Read MoreHow to terminate/destroy a process using Process API in Java 9?
In Java 9, Process API supports an easy way to get much information about a process. ProcessHandle interface can identify and provide the control of native processes and method to check processes liveness and destroy the processes whereas ProcessHandle.Info interface can give an Information snapshot of a process. We need to destroy a process by using the destroy() method of the ProcessHandle interface.In the below example, we need to terminate a process by using the ProcessHandle interface.Exampleimport java.io.File; import java.io.IOException; import java.util.Objects; public class DestroyProcessTest { public static void main(String[] args) throws InterruptedException { ...
Read MoreImportance of ofInstant() method in Java 9?
In Java 9, the ofInstant() method has introduced for conversion. It is a static method of LocalDate, LocalTime, and LocalDateTime classes. This method converts java.time.Instant object to LocalDate that requires a time zone in the form of java.time.ZoneId.Syntaxpublic static LocalTime ofInstant(Instant instant, ZoneId zone) public static LocalDate ofInstant(Instant instant, ZoneId zone) public static LocalDateTime ofInstant(Instant instant, ZoneId zone)Exampleimport java.time.LocalDate; import java.time.LocalTime; import java.time.LocalDateTime; import java.time.Instant; import java.time.ZoneId; public class OfInstantMethodTest { public static void main(String args[]) { Instant instant = Instant.parse("2020-02-05T02:35:15.245Z"); System.out.println("Instant: " + ...
Read MoreImportance of Collectors.flatMapping() method in Java 9?
In Java 9, a new method added to the Collectors class: flatMapping(). It is similar to the Collectors.mapping() method in which the flatMapping() method allows us to handle nested collections. The Collectors.flatMapping() method takes a function to be applied to input elements and a collector to accumulate the elements passed through the function. Unlike the Collectors.mapping() method, the Collectors.flatMapping() method deals with a stream of elements that allows us to get rid of unnecessary intermediary collections.Syntaxpublic static Collector flatMapping(Function
Read MoreImportance of the Collectors.filtering() method in Java 9?
Collectors class is an essential part of the Stream API. In Java 9, a new method: filtering() added to the Collectors class. The Collectors.filtering() method can be used for filtering elements in a stream. It is similar to the filter() method on streams. The filter() method processes the values before they have grouped whereas the filtering() method can be used nicely with the Collectors.groupingBy() method to group the values before the filtering step takes place.Syntaxpublic static Collector filtering(Predicate
Read MoreWhat is a forward reference in JShell in Java 9?
JShell is a command-line tool that allows us to enter Java statements (simple statements, compound statements, or even full methods and classes), evaluates it and prints the result.Forward references are commands that refer to methods, variables, or classes that don't exist in any code we have typed in JShell. As code entered and evaluated sequentially in JShell, these forward references have temporarily unresolved. JShell supports forward references in method bodies, return types, parameter types, variable types, and within a class.In the below code snippet, created a method forwardReference() in Jshell. This method can't be invoked until the variable is declared. ...
Read MoreHow to create JShell instance programmatically in Java 9?
JShell is an interactive tool introduced since Java 9. It is Java's first official REPL tool to create a simple programming environment in the command-line that reads the user's inputs, evaluates it, and prints the result.We can able to create a new JShell instance programmatically in Java language. JShell and its associated APIs can be found under jdk.jshell package. we can get a new instance for JShell by using the static method: create() of JShell class. The eval() method of JShell class used to add an expression to JShell instance. It returns a list of events triggered by the evaluation. ...
Read MoreWhat are the different shortcut keys in JShell in Java 9?
JShell is an interactive tool that allows us to execute the java code and getting immediate results. We quickly evaluate expressions or short algorithms without compiling or build it. We can execute expressions, classes, methods, variables, and etc with the help of the JShell tool.Below are some of the keyboard shortcut keys:Entrance - Validate the lineLeft arrow - Move left in the lineRight arrow - Move right in the lineCtrl-A - Move to the start of the lineCtrl-E- Move to the end of the lineAlt-B - Move left, word by wordAlt-F - Move right, word by wordDelete - Delete characters ...
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