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Programming Articles
Page 2322 of 2547
How can we add multiple sub-panels to the main panel in Java?
A JPanel is a subclass of JComponent class and it is an invisible component in Java. The FlowLayout is a default layout for a JPanel. We can add most of the components like buttons, text fields, labels, tables, lists, trees, etc. to a JPanel.We can also add multiple sub-panels to the main panel using the add() method of Container class.Syntaxpublic Component add(Component comp)Exampleimport java.awt.*; import javax.swing.*; public class MultiPanelTest extends JFrame { private JPanel mainPanel, subPanel1, subPanel2; public MultiPanelTest() { setTitle("MultiPanel Test"); ...
Read MoreHow can we set the border to JComboBox items in Java?
A JComboBox is a subclass of JComponent class and it is a combination of a text field and a drop-down list from which the user can choose a value. A JComboBox can generate an ActionListener, ChangeListener and ItemListener interfaces when the user actions on a combo box. We can set the border to the items of a JComboBox by rendering a JComboBox which extends the DefaultListCellRenderer class and need to override the getListCellRendererComponent() method.Syntaxpublic Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus)Exampleimport java.awt.*; import javax.swing.*; public class JComboBoxTest extends JFrame { public JComboBoxTest() { ...
Read MoreHow can we rotate a JLabel text in Java?
A JLabel is a subclass of JComponent class and an object of JLabel provides text instructions or information on a GUI. A JLabel can display a single line of read-only text, an image or both text and an image. A JLabel can explicitly generate a PropertyChangeListener interface. By default, JLabel can display a text in the horizontal position and we can rotate a JLabel text by implementing the rotate() method of Graphics2D class inside the paintComponent().Syntaxpublic abstract void rotate(double theta, double x, double y)Exampleimport java.awt.*; import java.awt.geom.*; import javax.swing.*; public class RotateJLabelTest extends JFrame { public RotateJLabelTest() ...
Read MoreHow many ways to iterate a LinkedList in Java?
A LinkedList is a data structure that contains a group of nodes connected in a sequential manner with a pointer. A LinkedList can behave as a dynamic array and it allocates space for each element separately in its own block of memory called a Node. Each node contains two fields, a "data" field to store an element type the list holds and a "next" field which is a pointer used to link one node to the next node.We can iterate the elements of a LinkedList in three ways in Java.Using IteratorWe can iterate the elements of a LinkedList through the ...
Read MoreWhat is the default value of a local variable in Java?
The local variables can be declared in methods, code blocks, constructors, etc in Java. When the program control enters the methods, code blocks, constructors, etc. then the local variables are created and when the program control leaves the methods, code blocks, constructors, etc. then the local variables are destroyed. The local variables do not have any default values in Java. This means that they can be declared and assigned a value before the variables are used for the first time, otherwise, the compiler throws an error.Examplepublic class LocalVariableTest { public void print() { ...
Read MoreHow can we add padding to a JTextField in Java?
A JTextField is a subclass of JTextComponent class and it is one of the most important components that allow the user to input text value in a single-line format. A JTextField class will generate an ActionListener interface when we trying to enter some input inside it. The important methods of a JTextField class are setText(), getText(), setBorder(), setEnabled(), etc. We can add padding to a JTextField using the setMargin(Insets s) of JTextComponent class.Syntaxpublic void setMargin(Insets m)Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; public class JTextfieldPaddingTest extends JFrame { private JTextField jtf; public JTextfieldPaddingTest() { ...
Read MoreHow to set the color to alternate rows of JTable in Java?
A JTable is a subclass of JComponent class and it can be used to create a table with information displayed in multiple rows and columns. When a value is selected from a JTable, a TableModelEvent is generated, which is handled by implementing a TableModelListener interface.We can set the color to alternate rows of JTable by overriding the prepareRenderer() method of JTable class.Syntaxpublic Component prepareRenderer(TableCellRenderer renderer, int row, int column)Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.table.*; public class AlternateRowColorTableTest extends JFrame { public AlternateRowColorTableTest() { setTitle("AlternateRowColorTable Test"); ...
Read MoreWhile chaining, can we throw unchecked exception from a checked exception in java?
When an exception is cached in a catch block, you can re-throw it using the throw keyword (which is used to throw the exception objects).While re-throwing exceptions you can throw the same exception as it is with out adjusting it as −try { int result = (arr[a])/(arr[b]); System.out.println("Result of "+arr[a]+"/"+arr[b]+": "+result); }catch(ArithmeticException e) { throw e; }Or, wrap it within a new exception and throw it. When you wrap a cached exception within another exception and throw it, it is known as exception chaining or, exception wrapping, by doing this you can adjust your exception, throwing higher ...
Read MoreWhen can a .class file get created in Java?
A Java class file has a ".class" extension and contains the Java bytecode. This class file can be executed by the Java Virtual Machine (JVM). A ".class" file is created as a result of successful compilation by the Java compiler from the ".java" file. Each class in the .java file is compiled into a separate class file if the ".java " file has more than one class.Exampleclass A { A() { System.out.println("This is class A"); } } class B { B() { ...
Read MoreIs there any method to convert a Set to immutable in Java
Whenever you need to create an object which cannot be changed after initialization you can define an immutable object. There are no specific rules to create immutable objects, the idea is to restrict the access of the fields of a class after initialization.A Set is an interface in collection framework, which does not allow duplicate values.Method to convert a set to immutableYes, Java provides a method named unmodifiableSet() in the Collections class. This method accepts a collection object as a parameter and returns an unmodifiable i.ie immutable form of it.ExampleIn the following Java program, we have created a HashSet object ...
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