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Articles by raja
Page 19 of 38
How can we write JSON objects to a file in Java?
The JSON is one of the widely used data-interchange formats and is a lightweight and language independent. The json.simple is a lightweight JSON processing library that can be used to write JSON files and it can be used to encode or decode JSON text and fully compliant with JSON specification(RFC4627). In order to read a JSON file, we need to download the json-simple.jar file and set the path to execute it.Exampleimport java.io.*; import java.util.*; import org.json.simple.*; import org.json.simple.parser.*; public class JSONObjectWriterToFileTest { public static void main(String[] args) throws IOException { JSONObject ...
Read MoreHow can we convert a JSON string to a JSON object in Java?
The JSON stands for JavaScript Object Notation and it can be used to transfer and storage of data. The JSONObject can parse text from a String to produce a map-like object. The object provides methods for manipulating its contents, and for producing a JSON compliant object serialization. The JSONArray can parse text from a String to produce a vector-like object. The object provides methods for manipulating its contents, and for producing a JSON compliant array serialization.In the below two examples, We can convert a JSON string to a JSON object.Example 1import org.json.JSONObject; import org.json.JSONArray; public class StringToJSONTest { ...
Read MoreHow to display a JFrame to the center of a screen in Java?
A JFrame is a subclass of Frame class and the components added to a frame are referred to as its contents, these are managed by the contentPane. We can add the components to a JFrame to use its contentPane instead. A JFrame is like a Window with border, title, and buttons. We can implement most of the java swing applications using JFrame.By default, a JFrame can be displayed at the top-left position of a screen. We can display the center position of JFrame using the setLocationRelativeTo() method of Window class.Syntaxpublic void setLocationRelativeTo(Component c)Exampleimport javax.swing.*; import java.awt.*; public class JFrameCenterPositionTest extends ...
Read MoreHow to display a JRadioButtonMenuItem in Java?
A JRadioButtonMenuItem is a subclass of the JMenuItem class in Java. A JRadioButtonMenuItem is a menu item that is part of a group of menu items in which only one item in the group can be selected and the selected item displays its selected state. We can add multiple radio button menu items to a ButtonGroup object to form a button group. If one radio button menu item in a button group is selected, all other radio button menu items will be unselected.Syntaxpublic class JRadioButtonMenuItem extends JMenuItem implements AccessibleExampleimport javax.swing.*; import java.awt.*; public class JRadioButtonMenuItemTest extends JFrame { private JMenuBar mb; ...
Read MoreWhen can we use the pack() method in Java?
The pack() method is defined in Window class in Java and it sizes the frame so that all its contents are at or above their preferred sizes. An alternative to the pack() method is to establish a frame size explicitly by calling the setSize() or setBounds() methods. In general, using the pack() method is preferable to call than setSize() method, since pack leaves the frame layout manager in charge of the frame size and layout managers are good at adjusting to platform dependencies and other factors that affect the component size.Syntaxpublic void pack()Exampleimport java.awt.*; import javax.swing.*; public class PackMethodTest extends JFrame { public ...
Read MoreHow can we apply different borders to JButton in Java?
A JButton is a subclass of AbstractButton class and it can be used for adding platform-independent buttons in a Java Swing application. A JButon can generate an ActionListener interface when the user clicking on a button, it can also generate MouseListener when a user can do some actions from the mouse and KeyListener when a user can do some actions from the keyboard.We can set different borders like LineBorder, BevelBorder, EtchcedBorder, EmptyBorder, TitledBorder, etc to JButton using the setBorder() method of JComponent class.Syntaxpublic void setBorder(Border border)Exampleimport javax.swing.*; import java.awt.*; public class JButtonBordersTest extends JFrame { private JButton ...
Read MoreHow 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 ...
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