Temperature Converter Program Using Java - Celsius, Kelvin, Fahrenheit, Reaumur and Rankine

Java Temperature Converter Program

A responsive and accurate temperature converter program can be made using java. In this post, we
will see a good temperature converter code. This java temperature conversion application converts temperature between Celsius, Kelvin, Fahrenheit, Reaumur and Rankine scales. The java program for this temperature consists of methods for:

• Celsius to Fahrenheit Conversion
• Celsius to Kelvin Conversion
• Celsius to Reaumur Conversion
• Celsius to Rankine Conversion
• Fahrenheit to Celsius Conversion
• Fahrenheit to Kelvin Conversion
• Fahrenheit to Reaumur Conversion
• Fahrenheit to Rankine Conversion
• Kelvin to Celsius Conversion
• Kelvin to Fahrenheit Conversion
• Kelvin to Reaumur Conversion
• Kelvin to Rankine Conversion
• Reaumur to Celsius conversion
• Reaumur to Kelvin conversion
• Reaumur to Fahrenheit conversion
• Reaumur to Rankine conversion
• Rankine to Celsius conversion
• Rankine to Kelvin conversion
• Rankine to Fahrenheit conversion
• Rankine to Reaumur conversion

Java Program to Send a File over a Network after Encryption

Here is a simple java program which can be used to send and receive encrypted files over network. The sender encrypts the file before sending and the receiver decrypts the file and displays it. The program is based on a networking lab experiment at my college. So, although we say 'encryption', characters are simply incremented here. The lab question was as follows:

A client wants a file that is with a server in a secure system. The server encrypts the file in such a way that 'A' will be replaced with 'B', 'B' with 'C'... and 'Z' with 'A' and sends to the client. The client should get file and decrypt it to the original one and display the content. Implement it using TCP/IP.

Java Program to Implement Broadcasting System Between a Server and Many Clients

Screenshot of broadcast server and clients using java

In this post we will see a java program which implements a broadcasting system. A Server can send a message as a multicast message into a multicast group. Any client can receive the multicasted packets after joining the group. The program make use of MulticastSocket class which is a subclass (derived class) of DatagramSocket class. Multicasting is almost same as UDP messaging. Datagram packets are used by MulticastSocket class. MulticastSocket class has two methods joinGroup() and leaveGroup(), each receive a InetAddress object as parameter which should be representing a multicast IP address. The datagrams sent using the MulticastSocket object should be addressed to a multicast group with IP between 224.0.0.0 and 239.255.255.255. These are IP addresses reserved for multicasting. The following java program to implement broadcasting using Multicast will tell you more.

How to Load a Webpage in a Java App

Do you wonder how to load a webpage in your java application? It is simple. You can load a web document whether it is a web document in internet or a web document from a file in the localhost. I know three methods to do it. You can use JTextPane in java swing (javax.swing), JEditorPane in java swing (javax.swing) or WebView in javaFX (javafx.scene.web.WebView). We will discuss each method to display a webpage in a java application.

The three methods we are going to discuss are:

• Using JTextPane
• Using JEditorPane
• Using WebView in JavaFX

Java FileNotFoundException While File is Existing There

Sometimes you my encounter a FileNotFoundException in java while you can see that the specified file is there. This can happen for several reasons.The java code may throw a  FileNotFoundException even when the file exists. This can be for different reasons.

Reason 1

The file does not exist really. Although you can see the file, the path you may have entered may be incorrect. For example, the following code may throw exception in some operating systems:

File f=new File("D:\myfile.txt");

This is because the file separator character is '\' in windows os. since \ is used to display non graphical characters like '\n' you should use its corresponding escape sequence. So "D:\\myfile.txt" would work on windows. If your java application is a cross platform program, you should consider using File.separator instead of '\\' because not all operating systems use '\\' as file separator character. So, the best approach is ;

File f=new File("D:"+File.separator+"myfile.txt");

File.separator is the system-dependent default name-separator character, represented as a string for convenience. This string contains a single character, namely File.separatorChar. If you want to get this character as a Character itself, you can use File.separatorChar. There can be other mistakes in the path.

Reason 2

The name you entered as a file may be actually a directory. So an exception can be thrown in java when you try to read from or write to such File object.

Reason 3

You cannot open it for reading or writing for some other reasons. You can check the status of file by calling the methods like f.exists(), f.canRead(), f.canWrite(), f.isFile() and f.isDirectory(). All these methods return a boolean. I hope these java method names describe well what they are intended for.

How to Filter Filetypes using File Extensions in JFileChooser - Java File Chooser

Screenshot of following example java program

In java, to browse files or folders from the file system, we use the JFileChooser class. You can use  the JFileChooser object in two modes, save mode or open mode. Here we discuss about filtering file type by file extensions for opening the file. By default, the JFileChooser object will have an AcceptAllFileFilter. This file filter will allow the user to select file of any file type. The file filter will display text All files. If you want to restrict the file chooser to open only one type of file, you should first remove the AcceptAllFileFilter. To do this, call the following method:

myfilechooser.removeChoosableFileFilter(createoropenchooser.getAcceptAllFileFilter());

What Does Modal and Modeless (Non Modal) Mean in Java

In java, the dialogue boxes in JOptionPane class are very popular. Now when we use dialogue boxes, whether it is message dialogue box, input dialogue or any other,  we may sometimes need to make the parent container (often JFrame or JWindow) not focusable. In another words, we may have to prevent a (parent) component taking input from the user while one of its member component is active. (You may have noticed that when error message boxes are displayed, you cannot click its parent window on many software until you dismiss it by clicking 'OK' or 'close'). Such a property of a member or child component, is called modality. In java, you can use JDialog with or without modality. A JDialog can be either modal or modeless.

A Modal dialog box is a dialog box that blocks input to some other top-level windows in the application. The modal dialog box captures the window focus until it is closed, usually in response to a button press.

A Modeless dialog box is a dialog box that does not block input to any other top level window while it is shown.

See following java code example:

How to Get User Related Informations in Java

In java, there are some methods that will help you to know some user related informations. Here also,

System.getProperty() 

method can give some informations about the user like:

User account name
User Working directory
User Home directory

To get the username of current user on the computer just call

System.getProperty("user.name")

It will return the current username as a string.

To get the working directory of current user on the computer call

System.getProperty("user.dir")

It will return the path of working directory of current user as a string.

To get the home directory (user's home folder) of current user on the computer call

System.getProperty("user.home")

It will return the path to home directory (folder) of current user as a string.

How to Get Operating System Information in Java

Using java, you can gather some information about the operating system of the computer system on which the code is running. That us java provides some API classes that will help you to know about the operating system of the computer on which your application program is running. You can use System.getProperty() method for this purpose. There are some system property keys (strings) which can be used to get the respective information. The parameter to the System.getProperty() method is a string, the property key. The following values for the parameter string will give operating system related informations.

"os.arch"
Operating system architecture

"os.name"
Name of the operating system.

"os.version"
Version of Operating system.

Usage examples:

The following java program displays the Operating system related informations using getProperty() method.

System.out.println("Operating system architecture:"+System.getProperty("os.arch") ); System.out.println("Operating system Name:"+System.getProperty("os.name") ); System.out.println("Operating system version:"+System.getProperty("os.version") );

How to Get JRE installation Directory in a Java Application

To get the java runtime environment (JRE) installation directory of a computer, we can use the getProperty() method in System class. The key to be used for System.getProperty() method to get the java JRE installation directory is "java.home". System.getProperty("java.home") will return the java runtime environment(JRE) installation directory path as a string. the following code will display the jre installation directory path:

System.out.println(System.getProperty("java.home"));