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Object Oriented Programming Articles
Page 322 of 589
Can we override a start() method in Java?
Yes! we can override the start() method of the Thread class in Java. But, if we do so, we must call it using super.start(), which will create a new thread; otherwise, no new thread will be created, and the run() method will not execute in parallel for the other threads. Overriding the start() Method In Java, the start() method is used to begin (start) the execution of a new Thread. When this method is called, it invokes the run() method, which executes in parallel with other threads. Example In the following example, we override the start() method within the subclass of ...
Read MoreGetting Started with C++ in Visual Studio
In this article, you will learn the setup to build and compile the C++ code in Visual Studio. Here you will become familiar with many of the tools and dialog boxes that you can use when you develop applications in C++. In this, we'll create a "Hello, World" style console application to help you learn more about working in this IDE. Prerequisites For this, you need a copy of Visual Studio 2017 version 15.3 or later, with the Desktop development with C++ workload installed. You can follow this guide to see the full installation procedure of Visual Studio [Link]. Create ...
Read MoreWhat are the differences between default constructor and parameterized constructor in Java?
The default and parameterized constructors are two types of Constructor in Java. The constructor is a special member of a Java class whose name is the same as the class name. It is used to assign values to a class variable at the time of object creation. In this article, we are going to discuss the difference between default and parameterized constructors. Default Constructor When we do not add a constructor to a Java class. The compiler adds a default constructor implicitly. It accepts 0 arguments. If we do not initialize the instance variables of a class, a default constructor will ...
Read MoreWhat are the different types of classes in Java?
In Java, a class is a datatype which defines properties (variables) and behaviors (methods) of an object. Defining an object does not consume memory; only its object or instance does.Depending on the requirement, we will create various types of classes in Java. In this article, we are going to discuss them. Types of classes in Java The Java class is classified into different types based on its methods, as shown in the list given below: Concrete class Abstract class Final class POJO class Static class Inner Class Wrapper Class Singleton Class Concrete class Any normal class which does ...
Read MoreWhat is the contract between equals() and hashCode() methods in Java?
Every Java object has two very important methods, equals() and hashCode(), and these methods are designed to be overridden according to their specific general contract. Since the Object class is the parent class of every class, the default implementation of the equals() and hashCode() methods is already present in each class. However, we need to override these methods based on the requirement. Let's discuss the contract between equals() and hashCode() methods in Java. But before that, we need to understand these methods. The hashCode() Method The hashCode() method returns an integer value, which is referred to as the hash code value ...
Read MoreInterface variables are static and final by default in Java, Why?
In Java, interfaces are used to achieve abstraction and multiple inheritance. They can contain methods and variables, but there are specific rules about how those members should behave. For example, all variables declared in an interface are public, static, and final by default, even if you don't use these keywords while defining variables. To understand the reason behind it, we first need to understand what static and final mean in Java. What is a Static Variable in Java? The static variables are defined using the static keyword. These variables belong to the class rather than to any specific object, which ...
Read MoreHow to handle the ArrayStoreException (unchecked) in Java?
In Java, ArrayStoreException is a public class that extends the RuntimeException class of the java.lang package. It is thrown by the Java Virtual Machine when a runtime error occurs. Since it is an unchecked exception, it does not require an explicit declaration in a method or a constructor's throws clause. Let's understand why the ArrayStoreException is thrown and how we can avoid it. Reason for ArrayStoreException in Java As mentioned earlier, ArrayStoreException is an unchecked exception, and it can occur when we try to store an object of one type in an array of a different type. Usually, one would ...
Read MoreHow to set local date/time in a table using LocalDateTime class in Java?
The java.time package of Java provides a class named LocalDateTime is used to get the current value of local date and time. Using this in addition to date and time values, you can also get other date and time fields, such as day-of-year, day-of-week, and week-of-year. Setting the Local time to a column To set the local date and time value to a column in a table. Obtain the LocalDateTime object: You can obtain the LocalDateTime object by invoking the static method now() as: LocalDateTime localDateTime = LocalDateTime.now(); Get the LocalDate and LocalTime objects from the above obtained LocalDateTime as: ...
Read MoreHow can we show a popup menu when the user right-clicks on a JComboBox in Java?
A JComboBox is a Swing component that has a built-in left-click menu. In this article, we will learn how to show a popup menu when the user right-clicks on a JComboBox in Java. What is a JComboBox? A JComboBox is a subclass of the JComponent class that displays a drop-down list and gives users options that they can select only one item at a time. A JComboBox can be editable or read-only. The getSelectedItem() Method A getSelectedItem() method can be used to get the selected or entered item from a combo box. What is a Popup Menu? A popup menu is ...
Read MoreHow to set the shortcut key to a JCheckBox in Java?
In this article, we will learn to set the shortcut key to a JCheckBox in Java. To create a JCheckBox with a keyboard shortcut (Alt + C), we will use Java Swing. When we either click the checkbox with the mouse or press Alt+C, the checkbox toggles, and a message dialog is displayed. We can do this by using the setMnemonic('C') method to assign the shortcut key and an ActionListener to respond to the checkbox selection. What is a JCheckBox? A JCheckBox is a subclass of JToggleButton, and it can be a small box that is either checked or unchecked. When ...
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