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Object Oriented Programming Articles
Page 492 of 589
What is the importance of JViewport class in Java?
JViewportA JViewport class defines the basic scrolling model and it is designed to support both logical scrolling and pixel-based scrolling.The viewport's child called the view is scrolled by calling JViewport.setViewPosition() method.A JViewport class supports logical scrolling, that is a kind of scrolling in which view coordinates are not pixels.To support a logical scrolling, JViewport defines a small set of methods that can be used to define the geometry of a viewport and a view. By default, these methods just report the pixel dimensions of the viewport and view.Exampleimport java.awt.*; import javax.swing.*; public class JViewportTest extends JFrame { public JViewportTest() { setTitle("JViewport Test"); ...
Read MoreWhat is the importance of a SwingWorker class in Java?
A SwingWorker class enables us to perform an asynchronous task in a worker thread (such as a long-running task) then update Swing components from the Event Dispatch Thread (EDT) based on the task results. It was introduced in Java 1.6 Version.SwingWorker classThe java.swing.SwingWorker class is a task worker, which performs time-consuming tasks in the background.A SwingWorker instance interacts with 3 threads, Current thread, the Worker thread, and the Event Dispatch thread(EDT).The Current thread calls the execute() method to kick off the task to the background and returns immediately.The Worker thread executes our own version of the doInBackground() method continuously in the background.The Event Dispatch Thread (EDT) wakes up from time to ...
Read MoreWhat are literals in C++?
A literal is any notation for representing a value within the source code. They just exist in your source code and do not have any reference a value in memory. Contrast this with identifiers, which refer to a value in memory.There are several types of literals in C++. Some of the examples of literals are −"Hello" (a string)3.141 (a float/double)true (a boolean)3 (an integer)'c' (a character)Things that are not literals −bar = 0; (a statement)3*5-4 (an expression)std::cin (an identifier)
Read MoreWhat is different between constant and variable in C++?
Variable and constant are two commonly used mathematical concepts. Simply put, a variable is a value that is changing or that have the ability to change. A constant is a value which remains unchanged.For example, if you have a program that has a list of 10 radii and you want to calculate the area for all of these circles. To find the area of these circles, you'll write a program that will have a variable that will store the value of PI and this value will not change throughout the program. Such values can be declared as a constant.In the ...
Read MoreWhat are different types of constants in C++?
There are no types of constants in C++. It's just that you can declare any data type in C++ to be a constant. If a variable is declared as constant using the const keyword, you cannot reassign its value. Example#include using namespace std; int main() { const int i = 5; // Now all of these operations are illegal and // will cause an error: i = 10; i *= 2; i++; i--; //... return 0; }
Read MoreHow to define constants in C++?
You can define constants in C++ by adding the const qualifier before the declaration of the variable. Example#include using namespace std; int main() { const int x = 9; x = 0; return 0; }This will define the constant variable x. But it will throw an error as we are trying to rewrite the value of a constant.
Read MoreHow to call an interface method in Java?
In order to call an interface method from a java program, the program must instantiate the interface implementation program. A method can then be called using the implementation object.Examplepublic interface InterfaceDemo{ default public void displayNameDefault(String name){ System.out.println("Your name is : " + name); } public void displayName(String name); public void displayNameAndDesignation(String name, String designation); }The above interface defines three methods for displaying a name and optionally a job title. One method is a default method that contains implementation logic. The remaining two methods do not include implementation logic.public class InterfaceDemoImpl ...
Read MoreWhat is type inference in C++?
Type inference or deduction refers to the automatic detection of the data type of an expression in a programming language. It is a feature present in some strongly statically typed languages. In C++, the auto keyword(added in C++ 11) is used for automatic type deduction. For example, you want to create an iterator to iterate over a vector, you can simply use auto for that purpose. Example#include #include using namespace std; int main() { vector arr(10); for(auto it = arr.begin(); it != arr.end(); it ++) { cin >> *it; } return 0; }In the ...
Read MoreHow do we initialize a variable in C++?
You can initialize a variable using the assignment operator or use its constructor when initializing it. For example,int i = 0; MyClass instance(1, "Hello");It will be automatically initialized ifIt's a class/struct instance in which the default constructor initializes all primitive types; like MyClass instance; You use array initializer syntax, e.g. int a[10] = {} (all zeroed) or int a[10] = {1,2}; (all zeroed except the first two items: a[0] == 1 and a[1] == 2) It is a global/extern variable It is defined static
Read MoreWhat does a semicolon do after a C++ class name?
If you have statements like −Class Person;This is a forward declaration. It lets the following code know that there is are classes with the name Person. This satisfies the compiler when it sees these names used. Later the linker will find the definition of the classes.
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