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Articles on Trending Technologies
Technical articles with clear explanations and examples
How can we implement a scrollable JPanel in Java?
JPanelA JPanel is a subclass of JComponent (a subclass of a Container class). Therefore, JPanel is also a Container.A JPanel is an empty area that can be used either to layout other components including other panels.In a JPanel, we can add fields, labels, buttons, checkboxes, and images also.The Layout Managers such as FlowLayout, GridLayout, BorderLayout and other layout managers helps us to control the sizes, positions, and alignment of the components using JPanel.The important methods of a JPanel class are getAccessibleContext(), getUI(), updateUI() and paramString().We can also implement a JPanel with vertical and horizontal scrolls by adding the panel object to JScrollPane.Exampleimport java.awt.*; ...
Read MoreHow can we implement editable JComboBox in Java?
JComboBoxA JComboBox can extend JComponent class and it is a combination of a text field and a drop-down list from which the user can choose a value.If the text field portion of the control is editable, the user can enter a value in the field or edit a value retrieved from the drop-down list.By default, the user not allowed to edit the data in the text field portion of the JComboBox. If we want to allow the user to edit the text field, call setEditable(true) method.A JComboBox can generate an ActionListener, ChangeListener or ItemListener when the user actions on a combo box.A ...
Read MoreHow can we find the duplicate values available in a MySQL table by using JOINS?
Suppose we have the following table named ‘stock_item’ in which the column quantity is having duplicate values i.e. for item name ‘Notebooks’ and ‘Pencil’, the column ‘Quantity’ is having duplicate values ‘40’ as shown in the table.mysql> Select * from stock_item; +------------+----------+ | item_name |quantity | +------------+----------+ | Calculator | 89 | | Notebooks | 40 | | Pencil | 40 | | Pens | 32 | | Shirts | 29 | | Shoes | ...
Read MoreHow can I use SPACE() function with MySQL WHERE clause?
In this case, SPACE() function would add white spaces depending upon the condition given in WHERE clause. The following example from student table will demonstrate it.Examplemysql> Select Id,Name,Space(5) from student WHERE Name='Harshit'; +------+---------+----------+ | Id | Name | Space(5) | +------+---------+----------+ | 15 | Harshit | | +------+---------+----------+ 1 row in set (0.00 sec)
Read MoreHow to implement a program to count the number in Java?
The program uses a JLabel to hold a count label, a JTextField component to hold the number count, JButton component to create add, remove and reset buttons. When we click the add button, the count in the JTextField will get incremented by '1' and by clicking the remove button the count will be decremented by '1'. If we click the Reset button, it will reset the count to '0'.Exampleimport java.awt.*; import java.awt.event.*; import javax.swing.*; public class CounterTest extends JFrame implements ActionListener { private JLabel label; private JTextField text; private JButton addBtn, ...
Read MoreHow many types of JDialog boxes can be created in Java?
A JDialog is a subclass of Dialog class and it does not hold minimize and maximize buttons at the top right corner of the window. We can create two types of JDialog boxes.in JavaModal DialogNon-Modal DialogModal JDialogIn Java, When a modal dialog window is active, all the user inputs are directed to it and the other parts of the application are inaccessible until this model dialog is closed.Non-Modal JDialogIn Java, When a non-modal dialog window is active, the other parts of the application are still accessible as normal and inputs can be directed to them, while this non-modal dialog window ...
Read MoreHow can we reverse a MySQL string connected by the dash?
MySQL has function name REVERSE() with the help of which we can reverse the string. But suppose if we want to reverse the string connected by dash then by using REVERSE() function will not give appropriate result as shown in the following example:mysql> Select REVERSE('AB-CD-EF'); +---------------------+ | REVERSE('AB-CD-EF') | +---------------------+ | FE-DC-BA | +---------------------+ 1 row in set (0.00 sec)The appropriate result would be ‘EF-CD-AB’ and for getting such output we can use SUBSTRING_INDEX() function along with Instr() function. It is demonstrated as follows:mysql> Select CONCAT(SUBSTRING_INDEX('AB-CD-EF', '-', -1), '-', substr('AB-CD-EF', instr('AB-CD-EF', "-")+1, instr('AB-CD-EF', "-")), LEFT('AB-CD-EF', ...
Read MoreHow can we write MySQL query for inner joins with the help of Comma operator?
Writing inner joins with the help of comma operator is the most basic way to combine two tables. As we know that we can also write inner join by using keyword INNER JOIN or synonyms like JOIN. To form an inner join we need to specify a particular condition which is known as join-predicate and while writing inner joins using the comma operator, we use WHERE clause, the only way, to specify the join condition. To understand it, we are taking the example of two tables named tbl_1 and tbl_2 which are having following data:mysql> Select * from tbl_1; +----+--------+ ...
Read MoreHow can we implement line wrap and word wrap text inside a JTextArea in Java?
A JTextArea is a multi-line text component to display text or allow the user to enter the text and it will generate a CaretListener interface when we are trying to implement the functionality of the JTextArea component. A JTextArea class inherits the JTextComponent class in Java.In the below example, we can implement a JTextArea class with a user can select either word wrap or line wrap checkboxes using the ItemListener interface.Exampleimport javax.swing.*; import java.awt.*; import java.awt.event.*; public class JTextAreaTest { public static void main(String[] args ) { EventQueue.invokeLater(new Runnable() { @Override public void run() { ...
Read MoreWhat is the importance of the GridBagConstraints class in Java?
A GridBagLayout is a very flexible layout manager that allows us to position the components relative to one another using constraints. Each GridBagLayout uses a dynamic rectangular grid of cells with each component occupying one or more cells called its display area. Each component managed by a GridBagLayout is associated with a GridBagConstraints instance that specifies how the component is laid out within its display area. GridBagConstraintsWe can customize a GridBagConstraints object by setting one or more of its public instance variables. These variables specify the component location, size, growth factor, anchor, inset, filling, and padding.gridx: An int value that specifies the leftmost cell that the ...
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