java socket connect read string

Java - create socket connection to HOST:PORT and read message from there

import java.io.*;
import java.net.*;
import java.util.*;

public class Time_Server_Socket_Test_Java {
    public static void main(String[] args) {
        try {
            Socket s = new Socket(HOST, PORT);//use your own HOST:PORT
            try {
                InputStream inStream = s.getInputStream();
                Scanner in = new Scanner(inStream);

                while (in.hasNextLine()) {
                    String line = in.nextLine();
                    System.out.println(line);
                }
            } finally {
                s.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

How to serialize variables selectively

In a Java class, one has 10 variables. One wants to serialize only 3 variables,how can this be achieved?
->Make variables as 'transient' which are not to be serialized.

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.

How Java packages organize code, prevent name collisions, and enforce access control.

Java packages act as a logical folder structure for your source code—java.lang, java.util, or a custom com.mycompany.util. They group related classes and sub-packages, making a large project modular and easy to navigate. Crucially, they provide a unique namespace that prevents naming conflicts: you can have your own Date class without clashing with java.util.Date because each sits in a different package. 

Beyond organization, the default package-private access level is a simple yet effective encapsulation feature. Any field or method declared without a modifier (public, protected, private) is visible only within the exact same package. This lets you hide internal helpers and data from outside code, protecting implementation details and ensuring that only authorized classes (those in the same package) can interact with sensitive members.

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

Wrapper Classes in Java – What Every Developer Should Know 

A wrapper class is a reference type that encapsulates a primitive value in an object. The Java standard library provides a dedicated wrapper for each of the eight primitive data types, as well as one for void. These classes reside in the java.lang package and are designed to bridge the gap between primitives and objects, enabling you to store primitive values in collections, work with generics, and use a wealth of utility methods for parsing, comparison, and conversion. Since Java 5, autoboxing and unboxing allow you to seamlessly convert between a primitive and its corresponding wrapper without explicit calls to valueOf() or xxxValue(), making the code cleaner while still relying on the underlying wrapper machinery.

The table below lists every primitive type alongside its immutable wrapper counterpart. Immutability means once a wrapper instance is created, its value cannot change – a critical property when using them as keys in maps or as elements in thread‑safe contexts. Common operations like conversion from a String (Integer.parseInt()), obtaining a wrapper instance (Boolean.valueOf(true)), and extracting the primitive (double d = dObj.doubleValue()) are all defined directly on these 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();
    }
});