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Articles by raja
Page 30 of 38
How to display all stack frames of the current thread in Java 9?
Stack Walking API can provide a flexible mechanism to traverse and extract information from call stacks that allow us to filter and access frames in a lazy manner. StackWalker class is an entry point to Stack Walking API. The stack trace is a representation of a call stack at a certain point of time in which each element represents a method invocation. It contains all invocations from the start of a thread until the point it’s generated.In the below example, we can print/display all stack frames of the current thread by using StackWalker API.Exampleimport java.lang.StackWalker.StackFrame; import java.lang.reflect.Method; import java.util.List; import java.util.stream.Collectors; public ...
Read MoreWhat is Variable Handle in Java 9?
Variable Handle is a variable or reference to a set of variables, including other components of a static field, non-static fields, and outer array elements in the heap data structure. It means that Variable Handle is similar to the existing Method Handle. It can be represented by using java.lang.invoke.VarHandle class. We can use java.lang.invoke.MethodHandles.Lookup static factory method to create Variable Handle objects. It can also be used to access a single element in the array, and byte[] array.Syntaxpublic abstract class VarHandle extends ObjectExampleimport java.lang.invoke.MethodHandles; import java.lang.invoke.VarHandle; import java.util.Arrays; public class VarHandleTest { public static void main(String ...
Read MoreWhat is the importance of the ProcessHandle interface in Java 9?
ProcessHandle interface introduced in Java 9. It allows us to perform actions and check the state of a process that relates. This interface provides the process’s native process ID (pid), start time, accumulated CPU time, arguments, command, user, parent process, and descendants.ProcessHandle interface allows us to perform the following actions.It returns a ProcessHandle.Info containing further information about a processThe Pid of a processIf it is aliveRetrieve a snapshot of the direct children of a processRetrieve a snapshot of all descents of a processRetrieve a snapshot of all currently running processesAllow the process to be destroyedIt returns a CompletableFuture with a ProcessHandle for when the ...
Read MoreWhat is Http/2 Client in Java 9?
Http/2 Client API introduced in Java 9. It has more performance improvements over Http/1.1 and also supports server-side push events. This makes the website efficient and faster to browse. Http/2 Client is an incubator module named jdk.incubator.httpclient, which means that all features are still not finalized, and new changes may come in future versions of java. It exports jdk.incubator.http package that contains all public APIs.To use Http/2 Client, we need to use the incubator module, we simply pass the httpclient module into JShell using the "–add-modules" command as belowC:\>jshell -v --add-modules jdk.incubator.httpclient | Welcome to JShell -- Version 9.0.4 | For an introduction type: /help introExamplejshell> import jdk.incubator.http.*; jshell> HttpClient httpClient ...
Read MoreHow to debug JShell in Java 9?
JShell is a REPL tool that allows snippets of code to be run without placing them in classes. This tool provides a way to evaluate declarations, statements, and expressions in Java and no need to create the main() method to test some parts of the code.The command "/debug" can be used to display debugging information for the JShell tool implementation. Once we type the "/debug" command, the debugging mode is on. After enabling the debug mode and type something like a simple addition, or a simple string, then it prints as below.Example-1jshell> /debug | Debugging on jshell> 5+3 Compiling: ...
Read MoreHow to implement a String in JShell in Java 9?
JShell is Java’s first official REPL application introduced in Java 9. It is a tool that helps in executing and evaluating simple java programs, and small logics such as statements, simple programs, loops, expressions, etc. Java REPL can provide a simple programming environment in a command-line prompt. It reads the input, evaluates it, and prints the output.In the below example, we can implement a string with pre-defined methods of String class.Examplejshell> String str = "{abcd}"; str ==> "{abcd}" jshell> str.substring(2, str.length() - 1) $7 ==> "bcd" jshell> String s1 = new String("abcd"); s1 ==> "abcd" jshell> String ...
Read MoreWhat is Common Locale Data Repository (CLDR) in Java 9?
Internationalization enhancements for Java 9 include enabling of CLDR Locale Data by Default.There are four distinct sources for locale data identified by using the below keywords:CLDR: The locale data provided by a Unicode Common Locale Data Repository (CLDR) project.HOST: The current user’s customization of an underlying operating system’s settings. Depending on the operating system, formats like date, time, number, and currency can be supported.SPI: The locale-sensitive services implemented in installed SPI providers.COMPAT (JRE): The locale data that is compatible with releases prior to Java 9. The JRE can still be used as a value but deprecated, and removed in the ...
Read MoreHow to implement an ArrayList using JShell in Java 9?
JShell is an interactive Java Shell tool that enables us to execute java code from the shell and instantly displays the output. JShell is the REPL(Read Evaluate Print Loop) tool that runs from the command-line. We can start a JShell by simply typing "jshell" in the command prompt, and to exit the jshell by using "/exit" command. For small snippets, we do not need to create a main() method in JShell.We can also implement the major collections like list, map and set by using this tool. In the below program, we can implement an ArrayList with various scenarios.ExampleC:\Users\User\Desktop\Java 9 QNA>jshell | Welcome to JShell ...
Read MoreWhat is Platform Logging API in Java 9?
In Java 9, Platform Logging API can be used to log messages with a service interface for consumers of those messages. An implementation of LoggerFinder has been loaded with the help of java.util.ServiceLoader API by using System ClassLoader. Based on this implementation, an application can plug in its own external logging backend without configuring java.util.logging.We can pass a class name or module to LoggerFinder so that it knows which logger to return.public class MyLoggerFinder extends LoggerFinder { @Override public Logger getLogger(String name, Module module) { // return a ...
Read MoreHow to filter stack frames using StackWalker API in Java 9?
StackWalker API provides a stream of information in stack traces during the execution of a program. This API requires a virtual machine to capture a snapshot of the entire stack and returns an array of elements for filtering purposes. We need to skip, drop, and limit the stack frames by using the walk() method. We can also filter a stack frame by class for getting the first matching frame, and all matching frames by using the filter() method.In the below example, we can filter a stack frame by using StackWalker API.Exampleimport java.lang.StackWalker.StackFrame; import java.util.*; import java.util.stream.*; public class StackWalkerFilterTest ...
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