Set environment variable for java

Setting up the environment in Java

Java is a general-purpose computer programming language that is concurrent, class-based, object-oriented, etc. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of computer architecture. The latest version is Java 19. Below are the environment settings for both Linux and Windows. JVM, JRE, and JDK three are all platform-dependent because the configuration of each Operating System is different. But, Java is platform-independent. Few things must be clear before setting up the environment which can better be perceived from the below image provided as follows:

• JDK(Java Development Kit): JDK is intended for software developers and includes development tools such as the Java compiler, Javadoc, Jar, and a debugger.
• JRE(Java Runtime Environment): JRE contains the parts of the Java libraries required to run Java programs and is intended for end-users. JRE can be viewed as a subset of JDK.
• JVM: JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides a runtime environment in which java bytecode can be executed. JVMs are available for many hardware and software platforms.

Now let us discuss the steps for setting up a Java environment with visual aids. Let’s use the Windows operating system to illustrate visual aids.

Steps: Here we will be proposing steps for three different operating systems as listed:

A. Windows operating systems

The steps for setting the environment in the Windows operating system are as follows:

Step 1: Java8 JDK is available at Download Java 8. Click the first link for Windows(32-bit) and the last link for Windows(64-bit) as highlighted below.

Step 2: Now you will see a download prompt just accept the term and conditions and click on the download button

Step 3: If you have an oracle account then sign in or if don’t then create one and sign in

Step 4: Then your download will start automatically after signing in if don’t then click on the previous link again

Step 5: After downloading, run the jdk-8u Application(.exe file) and follow the instructions to install Java on your machine. Once you install Java on your device, you have to set up the environment variable.

Step 6: Go to Control Panel -> System and Security -> System. Under the Advanced System Setting option click on Environment Variables as highlighted below.

Step 7: Now, you have to alter the “Path” variable under System variables so that it also contains the path to the Java environment. Select the “Path” variable and click on the Edit button as highlighted below.

Step 8: You will see a list of different paths, click on the New button, and then add the path where java is installed. By default, java is installed in “C:\Program Files\Java\jdk\bin” folder OR “C:\Program Files(x86)\Java\jdk\bin”. In case, you have installed java at any other location, then add that path.

Step 9: Click on OK, Save the settings, and you are done !! Now to check whether the installation is done correctly, open the command prompt and type javac -version. You will see that java is running on your machine.

Note: To make sure whether the compiler is set up, type javac in the command prompt. You will see a list related to javac.

B. Linux Operating System

In Linux, there are several ways to install java. But we will refer to the simplest and easy way to install java using a terminal. For Linux, we will install OpenJDK. OpenJDK is a free and open-source implementation of the Java programming language. Steps for setting the environment in the Linux operating system are as follows:

Step 1: Go to Application -> Accessories -> Terminal.

Step 2: Type the command as below as follows:

sudo apt-get install openjdk-8-jdk

Step 3: For the “JAVA_HOME” (Environment Variable) type the command as shown below, in “Terminal” using your installation path…(Note: the default path is as shown, but if you have to install OpenJDK at another location then set that path.)

export JAVA_HOME = /usr/lib/jvm/java-8-openjdk

Step 4: For “PATH” (Environment Value) type command as shown below, in “Terminal” using your installation path…Note: the default path is as shown, but if you have to install OpenJDK at another location then set that path.)

export PATH = $PATH:/usr/lib/jvm/java-8-openjdk/bin

Note: We are done setting up the environment in Java for Linux OS.

• Notepad/gedit : They are simple text-editors for writing java programs. Notepad is available on Windows and gedit is available on Linux.
• Eclipse IDE : It is the most widely used IDE(Integrated Development Environment) for developing software in java. You can download Eclipse.

C. MacOS Operating System

Step 1: Open the terminal from the application folder or simply press the “command” and “shift” key together and write initials of the terminal and press enter.

It will be good to have package manager such as homebrew installed in your machine as we can operate to install any software from here itself simply by using terminal commands.

Step 2: Now in order to configure first write the command ‘java –version ‘ where the message below it will pop that there is no

java --version javac --version

Note: If it was set up then you would have been getting the version displayed on the screen as it is shown below where in that machine it was already set up. So remember to cross-check in your machine once you have successfully set it up in yours.

Step 2: Once we are done with installing JDK now let us move on setting up the java_home environment variable for that you will have to look into something called s ‘bash_profie’ using the below command

You will notice that in your terminal there will be no bash_profile set but it is shown below so here in this machine it is already set up. In order to set it up if not there we have to create it which lets us prior seek into java home variables whether it is set up or not.

Step 3: Setting up the home java variable. Use the below command to check or setup if not installed as follows on the terminal:

If it is showing blank then the java home variable is not set up as perceived from the above image.

Step 4: Installing bash_profile

Make sure to go to the root folder in the terminal and write the command ‘touch ./bash_profile ‘

Now you will see that bash-profile s created which is as shown in the step2 in your machine which hone can verify by writing command as follows:

Step 5: Edit the .bash_profile created for java, you just have to write the command marked in below media and provided below as follows:

export JAVA_HOME=$(/usr/libexec/java_home) // No need to remember this command

Save this file and relaunch the terminal by closing it.

Step 5: Verifying whether it is installed by entering the following two commands

source .bash_profile echo $JAVA_HOME

From the above media, we can see the java variable is all set to go as earlier there was a blank therein the above media.

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Environment Variables

Many operating systems use environment variables to pass configuration information to applications. Like properties in the Java platform, environment variables are key/value pairs, where both the key and the value are strings. The conventions for setting and using environment variables vary between operating systems, and also between command line interpreters. To learn how to pass environment variables to applications on your system, refer to your system documentation.

Querying Environment Variables

On the Java platform, an application uses System.getenv to retrieve environment variable values. Without an argument, getenv returns a read-only instance of java.util.Map , where the map keys are the environment variable names, and the map values are the environment variable values. This is demonstrated in the EnvMap example:

import java.util.Map; public class EnvMap < public static void main (String[] args) < Mapenv = System.getenv(); for (String envName : env.keySet()) < System.out.format("%s=%s%n", envName, env.get(envName)); >> >

With a String argument, getenv returns the value of the specified variable. If the variable is not defined, getenv returns null . The Env example uses getenv this way to query specific environment variables, specified on the command line:

Passing Environment Variables to New Processes

When a Java application uses a ProcessBuilder object to create a new process, the default set of environment variables passed to the new process is the same set provided to the application’s virtual machine process. The application can change this set using ProcessBuilder.environment .

Platform Dependency Issues

There are many subtle differences between the way environment variables are implemented on different systems. For example, Windows ignores case in environment variable names, while UNIX does not. The way environment variables are used also varies. For example, Windows provides the user name in an environment variable called USERNAME , while UNIX implementations might provide the user name in USER , LOGNAME , or both.

To maximize portability, never refer to an environment variable when the same value is available in a system property. For example, if the operating system provides a user name, it will always be available in the system property user.name .

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How to set environment variables for Java using command line

Well, in this article I talked about the JVM, JRE and JDK, which are the cornerstones of the Java programming language. You develop Java applications by using tools like editors, IDEs and servers. These tools need to use the Java compiler ( javac ) and Java launcher ( java ) to compile and run Java applications, but these tools don’t know where the JRE or JDK is.

So, by setting up the environment variables, you tell your tools that:

“Hey, you can find the compiler and launcher here and there”.

The first thing you need to do after installing the JDK is creating an environment variable named JAVA_HOME and then update the PATH variable.

• JAVA_HOME : stores location of the JDK’s installation directory. When you install development tools, they will first check for the JAVA_HOME variable. If found, they will stick with it. If not, they may ask you to manually specify the location where JRE/JDK is installed.
• PATH : stores paths of directories where the operating system will look, to launch the requested programs quickly. For Java development, you should update this environment variable by adding an entry to the bin directory under JDK’s installation directory.

• JAVA_HOME = C:\Program Files\Java\jdk1.8.0
• PATH = PATH + C:\Program Files\Java\jdk1.8.0\bin

But that isn’t cool, because I’m about to show you how to do the same thing using command line prompt as shown below (Windows 7, 8 and 10):

setx JAVA_HOME "C:\Program Files\Java\jdk1.8.0" setx PATH "%PATH%;%JAVA_HOME%\bin";

The setx command permanently updates the environment variables. To add/update system environment variables, you must use the -m switch and open the command prompt using Administrator privilege: Click Start, type cmd . When the cmd.exe icon appears, right click and select Run as administrator.

To add/update system environment variables:

setx -m JAVA_HOME "C:\Program Files\Java\jdk1.8.0" setx -m PATH "%PATH%;%JAVA_HOME%\bin";

I prefer setting the environment variables using this command-line alternative. It’s quick and easy instead of going through several dialogs like using the GUI.

To summary, here are some important points:

• Always set JAVA_HOME when preparing development environment for Java.
• JAVA_HOME points to the installation directory of JDK.
• The PATH variable should contain an entry pointing to JAVA_HOME\bin .
• Environment can be set either via the GUI or command line prompt.

Related Tutorials:

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He started programming with Java in the time of Java 1.4 and has been falling in love with Java since then. Make friend with him on Facebook and watch his Java videos you YouTube.

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