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Java Articles
Page 300 of 450
How do you prevent a method from getting overridden in java?
Inheritance can be defined as the process where one (parent/super) class acquires the members (methods and fields) of another (child/sub).If two classes are related to each other with inheritance. If the super class and sub class contains same methods (same name and arguments), When we invoke this it using the sub class object, the method of the sub class will be executed. This mechanism is known as overriding.Overriding final methodsOnce you declare a method final it cannot be overridden If you try to do so, it generates a compile time error −Exampleclass Super{ public final void demo() { ...
Read MoreCan we call a constructor directly from a method in java?
A constructor is similar to method and it is invoked at the time creating an object of the class, it is generally used to initialize the instance variables of a class. The constructors have same name as their class and, have no return type.There is no need to invoke constructors explicitly these are automatically invoked at the time of instantiation.The this keyword in Java is a reference to the object of the current class. Using it, you can refer a field, method or, constructor of a class.Therefore, if you need to invoke a constructor explicitly you can do so, using "this()".Invoking a ...
Read MoreSequence of execution of, instance method, static block and constructor in java?
A static block is a block of code with a static keyword. In general, these are used to initialize the static members of a class. JVM executes static blocks before the main method at the time loading a class.Examplepublic class MyClass { static{ System.out.println("Hello this is a static block"); } public static void main(String args[]){ System.out.println("This is main method"); } }OutputHello this is a static block This is main methodA constructor is similar to method and it is invoked at the time creating an object of the class, it is ...
Read MoreWhat is diamond problem in case of multiple inheritance in java?
Inheritance is a relation between two classes where one class inherits the properties of the other class. This relation can be defined using the extends keyword as −public class A extends B{ }The class which inherits the properties is known as sub class or, child class and the class whose properties are inherited is super class or, parent class.In inheritance a copy of super class members is created in the sub class object. Therefore, using the sub class object you can access the members of the both classes.Multiple inheritanceThere are various types of inheritance available namely single, multilevel, hierarchical, multiple ...
Read MoreHow to make an object completely encapsulated in java?
The process of wrapping up the data and, the code acting on the data together is known as encapsulation. This is a protective mechanism where we hide the data of one class from (an object of) another.Since, variables hold the data of a class to encapsulate a class you need to declare the required variables (that you want to hide) private and provide public methods to access (read/write) them.By doing so, you can access the variables only in the current class, they will be hidden from other classes, and can be accessed only through the provided methods. Therefore, it is ...
Read MoreDoes java support hybrid inheritance?
Inheritance is a relation between two classes where one class inherits the properties of the other class. This relation can be defined using the extends keyword as −public class A extends B{ }The class which inherits the properties is known as sub class or, child class and the class whose properties are inherited is super class or, parent class.In inheritance a copy of super class members are created in the sub class object. Therefore, using the sub class object you can access the members of the both classes.Exampleclass Super{ int a =100; int b = 200; public void ...
Read MoreImportance of SerialVersionUID keyword in Java?\\n
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 InvalidClassException.If the serialVersionUID is ...
Read MoreHow can we call the invokeLater() method in Java?\\n
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(); System.out.println(name + ": " + msg); } ...
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"); button = new JButton("Rollover Button"); button.addMouseListener(new MouseAdapter() { ...
Read MoreImportance of the parseBoolean() method in Java?\\n
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 ...
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