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Java Articles
Page 354 of 450
What is the importance of SwingUtilities class in Java?
In Java, after swing components displayed on the screen, they can be operated by only one thread called Event Handling Thread. We can write our code in a separate block and can give this block reference to Event Handling thread. The SwingUtilities class has two important static methods, invokeAndWait() and invokeLater() to use to put references to blocks of code onto the event queue.Syntaxpublic static void invokeAndWait(Runnable doRun) throws InterruptedException, InvocationTargetException public static void invokeLater(Runnable doRun)The parameter doRun is a reference to an instance of Runnable interface. In this case, the Runnable interface will not be passed to the constructor of a Thread. The Runnable interface is simply ...
Read MoreWhat are the differences between JFrame and JDialog in Java?
JFrameThe components added to the frame are referred to as its contents, these are managed by the contentPane. To add a component to a JFrame, we must use its contentPane instead.A JFrame contains a window with title, border, (optional) menu bar and user-specified components.A JFrame can be moved, resized, iconified and it is not a subclass of JComponent.By default, JFrame is displayed in the upper-left corner of the screen. To display a frame at a specified location, we can use the setLocation(x, y) method in the JFrame class.Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; public class JFrameDemo { public static void main(String s[]) { ...
Read MoreWhy AWT components are heavy-weight while Swing components are light-weight in Java?
AWT stands for Abstract Window ToolKit and it supports Java GUI programming. It is a portable GUI library for Stand-alone Java applications/applets. The AWT provides the connection between our application and the native GUI while Java Swing implements a set of GUI components that build on AWT technology and it can provide a pluggable look and feel. Java Swing is implemented entirely in the Java programming language.First of all, by a heavy-weight, it means the code will take comparatively more time to load and it will consume more System resources. AWT is considered to be heavy-weight because its components are dependent ...
Read MoreWhy the constructor name is same as the class name in Java?
Every class object is created using the same new keyword, so it must have information about the class to which it must create an object. For this reason, the constructor name should be the same as the class name.Exampleclass MyConstructor{ public MyConstructor() { System.out.println("The constructor name should be same as the class name"); } public static void main(String args[]){ MyConstructor mc = new MyConstructor(); } }In the above program, the constructor name should be the same as the class name (MyConstructor).OutputThe constructor name should be same as the class name
Read MoreScope and lifetime of variables in Java?
Instance VariablesA variable which is declared inside a class and outside all the methods and blocks is an instance variable. The general scope of an instance variable is throughout the class except in static methods. The lifetime of an instance variable is until the object stays in memory.Class VariablesA variable which is declared inside a class, outside all the blocks and is marked static is known as a class variable. The general scope of a class variable is throughout the class and the lifetime of a class variable is until the end of the program or as long as the ...
Read MoreHow to access Java package from another package
You can understand it using an example where a Boss class is defined in payroll package.package payroll; public class Boss { public void payEmployee(Employee e) { e.mailCheck(); } }if the Employee class is not in the payroll package? The Boss class must then use one of the following techniques for referring to a class in a different package.The fully qualified name of the class can be used. For example −payroll.EmployeeThe package can be imported using the import keyword and the wild card (*). For example −import payroll.*;The class itself can be imported using the import ...
Read MoreHow to access Java package from another package
You can understand it using an example where a Boss class is defined in payroll package.package payroll; public class Boss { public void payEmployee(Employee e) { e.mailCheck(); } }if the Employee class is not in the payroll package? The Boss class must then use one of the following techniques for referring to a class in a different package.The fully qualified name of the class can be used. For example −payroll.EmployeeThe package can be imported using the import keyword and the wild card (*). For example −import payroll.*;The class itself can be imported using the import ...
Read MoreHow to access Java package from another package
You can understand it using an example where a Boss class is defined in payroll package.package payroll; public class Boss { public void payEmployee(Employee e) { e.mailCheck(); } }if the Employee class is not in the payroll package? The Boss class must then use one of the following techniques for referring to a class in a different package.The fully qualified name of the class can be used. For example −payroll.EmployeeThe package can be imported using the import keyword and the wild card (*). For example −import payroll.*;The class itself can be imported using the import ...
Read MoreHow to use sub-package in Java?
Subpackages are similar to sub-directories. Consider an example. The company had a com.apple.computers package that contained a Dell.java source file, it would be contained in a series of subdirectories like this −....\com\apple\computers\Dell.javaAt the time of compilation, the compiler creates a different output file for each class, interface, and enumeration defined in it. The base name of the output file is the name of the type, and its extension is .class.For example −// File Name:Dell.java package com.apple.computers; public class Dell { } class Ups { }Now, compile this file as follows using -d option −$javac -d.Dell.javaThe files will be compiled as ...
Read MoreHow to use sub-package in Java?
Subpackages are similar to sub-directories. Consider an example. The company had a com.apple.computers package that contained a Dell.java source file, it would be contained in a series of subdirectories like this −....\com\apple\computers\Dell.javaAt the time of compilation, the compiler creates a different output file for each class, interface, and enumeration defined in it. The base name of the output file is the name of the type, and its extension is .class.For example −// File Name:Dell.java package com.apple.computers; public class Dell { } class Ups { }Now, compile this file as follows using -d option −$javac -d.Dell.javaThe files will be compiled as ...
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