Linux hello world java

«Hello World!» for Solaris OS and Linux

It’s time to write your first application! These detailed instructions are for users of Solaris OS and Linux. Instructions for other platforms are in «Hello World!» for Microsoft Windows and «Hello World!» for the NetBeans IDE.

A Checklist

To write your first program, you’ll need:

The Java SE Development Kit 8 (JDK 8)

In this example, we’ll use Pico, an editor available for many UNIX-based platforms. You can easily adapt these instructions if you use a different text editor, such as vi or emacs .

These two items are all you’ll need to write your first application.

Creating Your First Application

Your first application, HelloWorldApp , will simply display the greeting «Hello world!». To create this program, you will:

Create a source file

A source file contains code, written in the Java programming language, that you and other programmers can understand. You can use any text editor to create and edit source files.

Compile the source file into a .class file

The Java programming language compiler ( javac ) takes your source file and translates its text into instructions that the Java virtual machine can understand. The instructions contained within this .class file are known as bytecodes.

The Java application launcher tool ( java ) uses the Java virtual machine to run your application.

Create a Source File

To create a source file, you have two options:

You can save the file HelloWorldApp.java on your computer and avoid a lot of typing. Then, you can go straight to Compile the Source File.

Or, you can use the following (longer) instructions.

First, open a shell, or «terminal,» window.

A new terminal window.

When you first bring up the prompt, your current directory will usually be your home directory. You can change your current directory to your home directory at any time by typing cd at the prompt and then pressing Return.

The source files you create should be kept in a separate directory. You can create a directory by using the command mkdir . For example, to create the directory examples/java in the /tmp directory, use the following commands:

To change your current directory to this new directory, you then enter:

Now you can start creating your source file.

Start the Pico editor by typing pico at the prompt and pressing Return. If the system responds with the message pico: command not found , then Pico is most likely unavailable. Consult your system administrator for more information, or use another editor.

When you start Pico, it’ll display a new, blank buffer. This is the area in which you will type your code.

Type the following code into the new buffer:

Be Careful When You Type

Note: Type all code, commands, and file names exactly as shown. Both the compiler ( javac ) and launcher ( java ) are case-sensitive, so you must capitalize consistently.

HelloWorldApp is not the same as helloworldapp .

Save the code in a file with the name HelloWorldApp.java . In the Pico editor, you do this by typing Ctrl-O and then, at the bottom where you see the prompt File Name to write: , entering the directory in which you wish to create the file, followed by HelloWorldApp.java . For example, if you wish to save HelloWorldApp.java in the directory /tmp/examples/java , then you type /tmp/examples/java/HelloWorldApp.java and press Return.

You can type Ctrl-X to exit Pico.

Compile the Source File into a .class File

Bring up another shell window. To compile your source file, change your current directory to the directory where your file is located. For example, if your source directory is /tmp/examples/java , type the following command at the prompt and press Return:

If you enter pwd at the prompt, you should see the current directory, which in this example has been changed to /tmp/examples/java .

If you enter ls at the prompt, you should see your file.

Results of the ls command, showing the .java source file.

Now are ready to compile the source file. At the prompt, type the following command and press Return.

The compiler has generated a bytecode file, HelloWorldApp.class . At the prompt, type ls to see the new file that was generated: the following figure .

Results of the ls command, showing the generated .class file.

Now that you have a .class file, you can run your program.

If you encounter problems with the instructions in this step, consult the Common Problems (and Their Solutions).

Run the Program

In the same directory, enter at the prompt:

The next figure shows what you should now see.

The output prints «Hello World!» to the screen.

Congratulations! Your program works!

If you encounter problems with the instructions in this step, consult the Common Problems (and Their Solutions).

Источник

Hello World in Java on Linux

This DrJava-based Java programming environment is no longer being supported (because DrJava in no longer being actively developed and DrJava is incompatible with Java 11). It has been replaced by the following IntelliJ-based programming environment for Linux.

This document instructs you on how to setup a Java programming environment under Linux. It also provides a step-by-step guide for creating, compiling, and executing your first Java program using either DrJava or the command line. We assume some familiarity with the command line. All of the software is freely available on the web.

You will use the Java Platform, Standard Edition Development Kit (JDK 8).

Log in to the user account in which you will be programming. Your account must have Administrator privileges and you must be connected to the Internet.

Launch your shell. We’ll assume that the command prompt looks like the following (though yours will likely differ):

/ is shorthand for your home directory.

Install the Java Platform, Standard Edition Development Kit (JDK 8), either from Oracle or OpenJDK. Most Linux distributions provide their own mechanism for installing software. For example, here are the commands on Ubuntu for Oracle JDK 8:

To confirm that the Java compiler is installed, type the command in boldface below and check that the results match:

To confirm that the Java interpreter is installed, type the command in boldface below and check that the results match:

1. Install a Programming Environment