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Articles on Trending Technologies
Technical articles with clear explanations and examples
Create translucent windows in Java Swing
With JDK 7, we can create a translucent window using swing very easily. With following code, a JFrame can be made translucent.// Set the window to 55% opaque (45% translucent). frame.setOpacity(0.55f);ExampleSee the example below of a window with 55% translucency.import java.awt.GridBagLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.SwingUtilities; public class Tester { public static void main(String[] args) { JFrame.setDefaultLookAndFeelDecorated(true); // Create the GUI on the event-dispatching thread SwingUtilities.invokeLater(new Runnable() { @Override public void ...
Read MoreCreate Toast Message in Java Swing
A toast message is an alert which disappears with time automatically. With JDK 7, we can create a toast message similar to an alert on android very easily. Following are the steps needed to make a toast message.Make a rounded rectangle shaped frame. Add a component listener to frame and override the componentResized() to change the shape of the frame. This method recalculates the shape of the frame correctly whenever the window size is changed.frame.addComponentListener(new ComponentAdapter() { @Override public void componentResized(ComponentEvent e) { frame.setShape(new RoundRectangle2D.Double(0, 0, frame.getWidth(), frame.getHeight(), 20, 20)); } ...
Read MoreCreate a simple calculator using Java Swing
Swing API is a set of extensible GUI Components to ease the developer's life to create JAVA based Front End/GUI Applications. It is built on top of AWT API and acts as a replacement of AWT API since it has almost every control corresponding to AWT controls.Following example showcases a simple calculator application.import java.awt.BorderLayout; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JTextField; public class Calculator implements ActionListener { private static JTextField inputBox; Calculator(){} public static void main(String[] args) { createWindow(); } ...
Read MoreHow can we add FOREIGN KEY constraints to more than one fields of a MySQL table?
MySQL allows us to add a FOREIGN KEY constraint on more than one field in a table. The condition is that each Foreign Key in the child table must refer to the different parent table.ExampleSuppose we have a table ‘customer2’ which have a Primary Key constraint on the field ‘cust_unq_id’ as follows −mysql> describe customer2; +-------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------------+-------------+------+-----+---------+-------+ | cust_id | int(11) | YES | | NULL | | | First_name | ...
Read MoreHow can we remove composite PRIMARY KEY constraint applied on multiple columns of an existing MySQL table?
We can remove composite PRIMARY KEY constraint from multiple columns of an existing table by using DROP keyword along with ALTER TABLE statement.ExampleSuppose we have a table ‘Room_allotment’ having a composite PRIMARY KEY constraint on columns ‘ID’ and ‘RoomNo’ as follows −mysql> describe room_allotment; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | id | int(11) | NO | PRI | 0 | ...
Read MoreHow can we set PRIMARY KEY on multiple columns of an existing MySQL table?
We can set PRIMARY KEY constraint on multiple columns of an existing table by using ADD keyword along with ALTER TABLE statement.ExampleSuppose we have a table ‘Room_allotment’ as follows −mysql> Create table Room_allotment(Id Int, Name Varchar(20), RoomNo Int); Query OK, 0 rows affected (0.20 sec) mysql> Describe Room_allotment; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | Id | int(11) | YES | | NULL | | | Name | varchar(20) | YES | | NULL ...
Read MoreHow to emulate a do-while loop in Python?
Python doesn't have an equivalent of do-while loop as in C/C++ or Java. The essence of do-while loop is that the looping condition is verified at the end of looping body. This feature can be emulated by following Python code −Examplecondition=True x=0 while condition==True: x=x+1 print (x) if x>=5: condition=FalseOutputThe output is as follows −1 2 3 4 5
Read MoreWhat happens if I will try to drop PRIMARY KEY constraint from the AUTO_INCREMENT column?
As we know the AUTO_INCREMENT column must have the PRIMARY KEY constraint on it also hence when we will try to drop PRIMARY KEY constraint from the AUTO_INCREMENT column the MySQL returns an error message regarding the incorrect table definition. The example below will demonstrate it −ExampleSuppose we have ‘Accounts’ table having the following description −mysql> Describe accounts; +--------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+----------------+ | Sr | int(10) | NO | PRI | NULL | auto_increment | ...
Read MoreHow can we remove PRIMARY KEY constraint from a column of an existing MySQL table?
We can remove PRIMARY KEY constraint from a column of an existing table by using DROP keyword along with ALTER TABLE statement.ExampleSuppose we have a table ‘Player’ having a PRIMARY KEY constraint on column ‘ID’ as follows −mysql> DESCRIBE Player; +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | ID | int(11) | NO | PRI | NULL | | | Name | varchar(20) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ 2 rows in ...
Read MoreHow can we apply the PRIMARY KEY constraint to the field of an existing MySQL table?
We can apply the PRIMARY KEY constraint to a column of an existing MySQL table with the help of ALTER TABLE statement. SyntaxALTER TABLE table_name MODIFY colum_name datatype PRIMARY KEY; OR ALTER TABLE table_name ADD PRIMARY KEY (colum_name); Suppose we have the following table named ‘Player’ and we want to add the PRIMARY KEY constraint to the column ‘ID’ then it can be done with the help of ALTER TABLE command as follows −mysql> DESCRIBE Player; +-------+-------------+------+-----+---------+-------+ | Field | Type ...
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