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Java Articles
Page 302 of 450
Importance of SerialVersionUID keyword in Java?
SerialVersionUIDThe SerialVersionUID must be declared as a private static final long variable in Java. This number is calculated by the compiler based on the state of the class and the class attributes. This is the number that will help the JVM to identify the state of an object when it reads the state of the object from a file.The SerialVersionUID can be used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible w.r.t serialization. If the deserialization object is different than serialization, then it can throw an ...
Read MoreHow 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 MoreCan we override final methods in Java?
Overriding is a one of the mechanisms to achieve polymorphism. This is the case when we have two classes where, one inherits the properties of another using the extends keyword and, these two classes same method including parameters and return type (say, sample).Since it is inheritance. If we instantiate the subclass a copy of superclass’s members is created in the subclass object and, thus both methods are available to the subclass.When we invoke this method (sample) JVM calls the respective method based on the object used to call the method.Overriding final methodsNo, you cannot override final method in java. If ...
Read MoreJava.util.StringJoiner in Java8
This class is used Join a sequence of characters separating using the delimiter.Examplepublic class StringJoinerSample { public static void main(String[] args){ StringJoiner sj = new StringJoiner(", "); sj.add("Krishna"); sj.add("Raju"); sj.add("Satish"); sj.add("Pruthvi"); System.out.println(sj); } }OutputKrishna, Raju, Satish, Pruthvi
Read MoreWhat is the difference between object and reference in java?
A class in a blue print/user defined datatype in java that describes the behavior/state that the object of its type support.Examplepublic class Student { String name "Krishna"; int age = 20; void greet() { System.out.println("Hello how are you"); } }An object is an instance of a class created from it using the new keyword. Once you create an object of a class, using it you can access he members of the class. In the below given code an object of the class Student is created.public class Example { public static void main(String ...
Read MoreCan we serialize static variables in Java?
In Java, serialization is a concept using which we can write the state of an object into a byte stream so that we can transfer it over the network (using technologies like JPA and RMI).But, static variables belong to class therefore, you cannot serialize static variables in Java. Still if you try to do so, the program gets compiled successfully but it raises an exception at the time of execution.In the following java program, the class Student has a static variable and we are trying to serialize and desterilize its object in the another class named ExampleSerialize.Exampleimport java.io.FileInputStream; import java.io.FileOutputStream; ...
Read MoreExplain how to remove Leading Zeroes from a String in Java
Whenever you read an integer value into a String, you can remove leading zeroes of it using StringBuffer class, using regular expressions or, by converting the given String to character array.Converting to character arrayFollowing Java program reads an integer value from the user into a String and removes the leading zeroes from it by converting the given String into Character array.Exampleimport java.util.Scanner; public class LeadingZeroes { public static String removeLeadingZeroes(String num){ int i=0; char charArray[] = num.toCharArray(); for( ; i
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