maximize a JFrame window in java

How to Maximize a JFrame :

 
    JFrame myFrame = new JFrame();
    myFrame.setVisible(true);
    myFrame.setExtendedState(myFrame.getExtendedState() | JFrame.MAXIMIZED_BOTH);
    

The usage of Java packages.

Explain the usage of Java packages.

A. This is a way to organize files when a project consists of multiple modules. It also helps resolve naming conflicts when different packages have classes with the same names. 

Packages access level also allows you to protect data from being used by the non-authorized classes.

Java: difference between private, protected, and public?

These keywords are for allowing privileges to components such as java methods and variables.
Public: accessible to all classes
Private: accessible only to the class to which they belong
Protected: accessible to the class to which they belong and any subclasses.

Access specifiers are keywords that determines the type of access to the member of a class. These are:
* Public
* Protected
* Private
* Defaults

java show window JFrame JDialog always on top

We have to use this feature of java.awt.Window : Window.alwaysOnTop(boolean); Example code :

import javax.swing.JFrame;
import javax.swing.JLabel;

public class Always_on_Top_JFrame_JAVA{
    public static void main(String[] args) {
        JFrame frame = new JFrame("Title - always on top :D ");
        // Set's the window to be "always on top"
        frame.setAlwaysOnTop( true );

        frame.setLocationByPlatform( true );
        frame.add( new JLabel(" Always on TOP ") );
        frame.pack();
        frame.setVisible( true );
    }
}

Order of catching exception in java

Does it matter in what order catch statements for FileNotFoundException and IOExceptipon are written?

A. Yes, it does. The FileNotFoundException is inherited from the IOException. 

Exception's subclasses have to be caught first.

Exception

^

|

IOException

^

|

FileNotFoundException 

So while catching exceptions, we must catch the low level exception first - here : FileNotFoundException .

#The hierarchy in Java Exception framework :

wrapper classes in Java

Describe the wrapper classes in Java.Wrapper class is wrapper around a primitive data type. An instance of a wrapper class contains, or wraps, a primitive value of the corresponding type.

Following table lists the primitive types and the corresponding wrapper classes:

Primitive - Wrapper

boolean  - java.lang.Boolean

byte - java.lang.Byte

char - java.lang.Character

double - java.lang.Double

float - java.lang.Float

int - java.lang.Integer

long - java.lang.Long

short - java.lang.Short

void - java.lang.Void

Java Class as Applet as well as Application

Can you write a Java class that could be used both as an applet as well as an application?
A. Yes. Add a main() method to the applet.

Bring JFrame JDialog Window to front java swing

To bring JFrame or JDialog ... or Window (JFrame and JDialog inherits Window)   to front in JAVA, fun the code below :

java.awt.EventQueue.invokeLater(new Runnable() {
    @Override

    //myFrame is object of Window or JFrame
    public void run() {
        myFrame.toFront();
        myFrame.repaint();
    }
});

Redirect Standard System Output and Error Message to PrintStream in Java

In a Java program, how can you divert standard system output or error messages, say to a file?
->We can achieve this by using
public static void setErr(PrintStream err)
and public static void setOut(PrintStream out) methods.
By default, they both point at the system console. The following example redirects Out and Err messages to 'error.txt'  file

Stream stream = new Stream(new FileOutputStream("error.txt"));
System.setErr(stream);
System.setOut(stream);

You can redirect the Err and Out stream to any PrintStream object.

concatenate arrays of any type - java

Combining two arrays of any type

 public static  T[] concat(T[] first, T[] second) {
  T[] result = Arrays.copyOf(first, first.length + second.length);
  System.arraycopy(second, 0, result, first.length, second.length);
  return result;
 }

For combining arbitrary number of arrays