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Articles by raja
Page 21 of 38
How can we call the invokeLater() method in Java?
An invokeLater() method is a static method of the SwingUtilities class and it can be used to perform a task asynchronously in the AWT Event dispatcher thread. The SwingUtilities.invokeLater() method works like SwingUtilities.invokeAndWait() except that it puts the request on the event queue and returns immediately. An invokeLater() method does not wait for the block of code inside the Runnable referred by a target to execute.Syntaxpublic static void invokeLater(Runnable target)Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; public class InvokeLaterTest extends Object { private static void print(String msg) { String name = Thread.currentThread().getName(); ...
Read MoreHow to implement a rollover effect for a JButton in Java?
A JButton is a subclass of AbstractButton and it can be used for adding platform-independent buttons to a GUI application. A JButon can generate an ActionListener interface when the button is pressed or clicked, it can also generate the MouseListener and KeyListener interfaces. We can implement the rollover effect when the mouse moves over a JButton by overriding the mouseEntered() method of the MouseListener interface.Syntaxvoid mouseEntered(MouseEvent e)Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; public class RollOverButtonTest extends JFrame { private JButton button; public RollOverButtonTest() { setTitle("RollOverButton Test"); ...
Read MoreImportance of the parseBoolean() method in Java?
The parseBoolean() method is an important method of a Boolean class. The parseBoolean() is a static method and can parse the String method argument into a Boolean object. The parseBoolean() method of Boolean class returns the boolean represented by the string argument.Syntaxpublic static boolean parseBoolean(String s)Exampleimport java.util.Scanner; public class ParseBooleanMethodTest { public static void main(String[] args) { System.out.print("Are you ready to play cricket(true/false)?"); Scanner scanner = new Scanner(System.in); String str = scanner.nextLine(); scanner.close(); // Convert the user input into boolean boolean answer ...
Read MoreWhat is the importance of a WindowListener interface in Java?
The class which process the WindowEvent needs to be implemented this interface and an object of this class can be registered with a component by using addWindowListener() method.Methods of WindowListener InterfaceThe WindowListener interface defines 7 methods for handling window eventsvoid windowActivated(WindowEvent we) − Invoked when a window is activated.void windowDeactivated(WindowEvent we) − Invoked when a window is deactivated.void windowOpened(WindowEvent we) − Invoked when a window is opened.void windowClosed(WindowEvent we) − Invoked when a window is closed.void windowClosing(WindowEvent we) − Invoked when a window is closing.void windowIconified(WindowEvent we) − Invoked when a window minimized.void windowDeiconfied(WindowEvent we) − Invoked when a window is restored.Syntaxpublic ...
Read MoreHow to print pid, info, children, and destroy processes in JShell in Java 9?
JShell is a Java Shell tool used to execute simple java statements like classes, methods, interfaces, enums, and etc.. evaluates it, and prints the result in a command-line prompt.Java has improved Process API to manage and control operating system processes. ProcessHandle interface identifies and provides control of native processes, methods to check processes liveness, and destroy the process. ProcessHandle.Info interface gives an Information snapshot of a process.In the below code snippet, we can print pid, info, children, and destroy processes of Process API.in JShell tool.Snippetjshell> ProcessHandle currentProcess = ProcessHandle.current(); currentProcess ==> 3960 jshell> System.out.println("Current Process Id: = " + currentProcess.pid()); Current Process Id: = 3960 jshell> ...
Read MoreHow to get system properties in JShell in Java 9?
JShell is a REPL (Read-Evaluate-Print-Loop) tool used to execute simple statements, evaluates it, and displays the result without a main() method. We can start it by simply type "jshell" in command-line prompt.We need to get the system properties by using System.getProperty() and System.getProperties() methods.In the below code snippet, we can able to display the system properties in the JShell tool by using static method property() of System class.Snippet-1jshell> System.getProperty("java.class.path") $1 ==> "C:\Program Files\Java\jdk-9.0.4\lib;C:\json-jars\json.jar;.;C:\json-jars\json-simple.jar;.;C:\json-jars\gson.jar;.;C:\json-jars\commons-io.jar;.;C:\json-jars\jackson-core.jar;.;C:\json-jars\jackson-databind.jar;.;C:\json-jars\jackson-annotations.jar;.;C:\json jars\flexjson.jar;.;C:\json-jars\jackson-dataformat-xml.jar;.;C:\json-jars\stax2-api.jar;.;C:\json-jars\jackson-dataformat-csv.jar;.;C:\json-jars\javax.json.jar;.;C:\json jars\javax.json-api.jar;.;C:\json-jars\jackson-module-jsonSchema.jar;.;C:\json-jars\json-lib.jar;.;C:\json-jars\commons-lang.jar;.;C:\json-jars\commons-logging.jar;.;"In the below code snippet, we have to use the “properties” object that extends Hashtable. So all properties can be listed as key/value pairs in the JShell tool by using ...
Read MoreHow to implement JShell using JavaFX in Java 9?
JShell is an interactive tool used to implement sample expressions. We can implement JShell programmatically using JavaFX application then we need to import a few packages in the java program listed belowimport jdk.jshell.JShell; import jdk.jshell.SnippetEvent; import jdk.jshell.VarSnippet;In the below example, implemented a sample Java FX application. We will enter different values in the text field and press the "eval" button. It will display values with corresponding data types in a list.Exampleimport javafx.application.Application; import javafx.scene.Scene; import javafx.scene.control.*; import javafx.scene.layout.*; import javafx.stage.Stage; import java.util.List; import jdk.jshell.JShell; import jdk.jshell.SnippetEvent; import jdk.jshell.VarSnippet; public class JShellFXTest extends Application { @Override public void start(Stage primaryStage) ...
Read MoreHow to implement HashMap, LinkedHashMap, and TreeMap in JShell in Java 9?
JShell is a command-line prompt tool introduced in Java 9, and it is also called a REPL tool to evaluate simple statements, executes it, and print the output immediately.A Map interface specifies a contract to implement collections of elements in the form of key/value pairs. Java collection classes that implement the Map interface are HashMap, LinkedHashMap, and TreeMap.In the below code snippet, the elements of HashMap are not guaranteed to store either in an insertion order or in the sorted order of keys.Snippet-1jshell> HashMap hashMap = new HashMap(); hashMap ==> {} jshell> hashMap.put("Adithya", 101); $2 ==> null jshell> ...
Read MoreDifferences between CompletableFuture and Future in Java 9?
CompletableFuture class implements Future interface in Java. CompletableFuture can be used as a Future that has explicitly completed. The Future interface doesn’t provide a lot of features, we need to get the result of asynchronous computation using the get() method, which is blocked, so there is no scope to run multiple dependent tasks in a non-blocking fashion whereas CompleteFuture class can provide the functionality to chain multiple dependent tasks that run asynchronously, so we can create a chain of tasks where the next task is triggered when the result of the current task is available.Syntaxpublic class CompletableFuture extends Object implements ...
Read MoreHow to get a snapshot of information about Process API in Java 9?
Java 9 has improved Process API by including new methods and introduced new interfaces ProcessHandle and ProcessHandle.Info to get all the details regarding the process and its information.ProcessHandle interface can identify and provide control of native processes. Each individual process can be monitored for liveness, listed its children, get information about the process, or destroys it. ProcessHandle.Info interface gives information snapshots about a process.SyntaxProcessHandle.Info info()Examplepublic class ProcessSnapShotTest { public static void main(String[] args) { ProcessHandle currentProcessHandleImpl = ProcessHandle.current(); ...
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