Setting up enviromental variables in Windows 10 to use java and javac

I got a new laptop with Windows 10 and I want to set it up so I can use java and javac from the command line.

I have searched online but all the guides are for previous versions, and I don’t want to mess around with something I don’t understand.

7 Answers 7

Just set the path variable to JDK bin in environment variables.

But the best practice is to set JAVA_HOME and PATH as follow.

Here are the typical steps to set JAVA_HOME on Windows 10.

1. Search for Advanced System Settings in your windows Search box. Click on Advanced System Settings.
2. Click on Environment variables button: Environment Variables popup will open.
3. Goto system variables session, and click on New button to create new variable (HOME_PATH), then New System Variables popup will open.
4. Give Variable Name: JAVA_HOME, and Variable value : Your Java SDK home path. Ex: C:\Program Files\java\jdk1.8.0_151 Note: It should not include \bin. Then click on OK button.
5. Now you are able to see your JAVA_HOME in system variables list. (If you are not able to, try doing it again.)
6. Select Path (from system variables list) and click on Edit button, A new pop will opens (Edit Environment Variables). It was introduced in windows 10.
7. Click on New button and give %JAVA_HOME%\bin at highlighted field and click Ok button.

You can find complete tutorials on my blog :

How to set system variables from Java?

I need to set certain system variables from within the program. My Google fu is failing me in finding any way to do it. How do I do it? (I am okay with hacky approaches. I need to be able to run this app on Windows, Linux, and Mac.)

Edit:

Adding here my comment from below the post, as it isn’t readily visible there:

The best link I could found was this, and it sets the variables only in memory. They do not persist after the program exit.

Edit:

I am writing an installer and need to somehow record at system level that installation happened (along with paths to some directories). The next time user runs the setup, the installer will check if the variables already exist in the system, in which case a user will be given an appropriate warning.

If twiddling with environment variables is not a good idea, what will be the best approach to achieve the above?

6 Answers 6

If you want your environment variables to persist after your program ends, I would suggest you use the Properties class. It can be persisted to a file very easily, and vice versa.

Use following methods of system class

for more details reffer

First of all, Properties is a java class that is used to hold properties that maybe needed for your program. The basic properties that you are talking about are provided by the operating system. Not all of these can be changed. If you try, you will get a SecutrityException (You can’t change the os.name for instance). The basic properties are read from the memory of the computer (basically) you can add additional variables to this by setting environment variables in the operating system you are using. Such as in Win95 you can add to the autoexec.bat the line: set BARTENDER_NAME=Carl This line can go in any batch file and BARTENDER_NAME will equal Carl until you reset it. In your java program If you add the line System.out.println(System.getProperty(«BARTEDER_NAME»)); You’ll get Carl as the output. In the bash shell on Linux or Unix you’d use BARTENDER_NAME=Carl export BARTENDER_NAME

You can create your own set of properties for your java program and store them in a file and load them using the Properties load() method. Hope this helps

Ok this is off the top of my head so it’s extremely hacky and stuff.

Get hold of a process and run the command line command that will set the system variables. This isn’t portable but it should suffice for short term till you find a better solution.

Because there is not a standard solution for this, I would recommend you to use a Factory Pattern for this. It means something like:

if system is Windows

else if system is Linux

else if system is Mac

and the persistEnvironment method would call the specific functions on EnvManager .

Environment variables for java installation

How to set the environment variables for Java in Windows (the classpath)?

14 Answers 14

Java SE Development Kit 8u112 on a 64-bit Windows 7 or Windows 8

Set the following user environment variables (== environment variables of type user variables)

• JAVA_HOME : C:\Program Files\Java\jdk1.8.0_112
• JDK_HOME : %JAVA_HOME%
• JRE_HOME : %JAVA_HOME%\jre
• CLASSPATH : .;%JAVA_HOME%\lib;%JAVA_HOME%\jre\lib
• PATH : your-unique-entries;%JAVA_HOME%\bin (make sure that the longish your-unique-entries does not contain any other references to another Java installation folder.

Note for Windows users on 64-bit systems:

Notice that these environment variables are derived from the «root» environment variable JAVA_HOME . This makes it easy to update your environment variables when updating the JDK. Just point JAVA_HOME to the fresh installation.

Optional recommendations

• Add an user environment variable JAVA_TOOL_OPTIONS with value -Dfile.encoding=»UTF-8″ . This ensures that Java (and tools such as Maven) will run with a Charset.defaultCharset() of UTF-8 (instead of the default Windows-1252 ). This has saved a lot of headaches when wirking with my own code and that of others, which unfortunately often assume the (sane) default encoding UTF-8.
• When JDK is installed, it adds to the system environment variable Path an entry C:\ProgramData\Oracle\Java\javapath; . I anecdotally noticed that the links in that directory didn’t get updated during an JDK installation update. So it’s best to remove C:\ProgramData\Oracle\Java\javapath; from the Path system environment variable in order to have a consistent environment.

In Windows inorder to set

Step 1 : Right Click on MyComputer and click on properties .

Step 2 : Click on Advanced tab

Step 3: Click on Environment Variables

Step 4: Create a new class path for JAVA_HOME

Step 5: Enter the Variable name as JAVA_HOME and the value to your jdk bin path ie c:\Programfiles\Java\jdk-1.6\bin and

NOTE Make sure u start with .; in the Value so that it doesn’t corrupt the other environment variables which is already set.

Step 6 : Follow the Above step and edit the Path in System Variables add the following ;c:\Programfiles\Java\jdk-1.6\bin in the value column.

Step 7 :Your are done setting up your environment variables for your Java , In order to test it go to command prompt and type

who will get a list of help doc

In order make sure whether compiler is setup Type in cmd

who will get a list related to javac

Hope this Helps !

— To set java path —

There are two ways to set java path

A. Temporary

1. Open cmd
2. Write in cmd : javac

If java is not installed, then you will see message:

javac is not recognized as internal or external command, operable program or batch file.

1. Write in cmd : set path=C:\Program Files\Java\jdk1.8.0_121\bin
2. Write in cmd : javac

You can check that path is set if not error has been raised.

It is important to note that these changes are only temporary from programs launched from this cmd.

NOTE: You might have to run the command line as admin

B. Permanent

1. Righ-click on «My computer» and click on properties
2. Click on «Advanced system settings»
3. Click on «Environment variables»
4. Click on new tab of user variable
5. Write path in variable name
6. Copy the path of bin folder
7. Paste the path of the bin folder in the variable value
8. Click OK

The path is now set permanently.

TIP: The tool «Rapid Environment Editor» (freeware) is great for modifying the environment variables and useful in that case

Is it possible to set an environment variable at runtime from Java?

Is it possible to set an environment variable at runtime from a Java application? In Java 1.5 java.lang.System class there is the getenv() method, I would only need a setenv() method.

Is it possible to modify the environment variables in the java process itself; not in the child process.

Is it possible to achieve it through JNI? And how would that work?

EDIT: Ok let me put it this way — Can we do the following with Java. Please answer.

1. Can we modify the environment of the current process?
2. Can we modify the environment of the parent process?
3. Can we modify the environment of the child process?

Hemal Pandya has answered that «You can modify the environment of current and child processes but not of the parent process that spawned this process.» Do you agree with this ?

6 Answers 6

If my intuition is correct, and you actually want to modify the environment for the benefit of a spawned (forked) sub-process ( Runtime.getRuntime().exec() ), then use ProcessBuilder instead of exec() . You can build a custom environment via your ProcessBuilder instance’s environment() method.

If this is not what you are trying to achieve then kindly disregard this answer.

UPDATE

The answer to your three updated, specific questions is as follows:

1. Can we modify the environment of the current process?
   • Not easily. Depends whether you want to change the process’ environment, to change the value(s) returned by System.getenv() in the same JVM, or both.
   • As Greg Hewgill pointed out, to change the current process’ environment you can call setenv or its platform-specific equivalent via JNI. You may also employ the extremely convoluted method from point 2 below, which works for any process (provided you have the permissions.) However, be aware that in most JVMs this change might never be reflected in the values returned by System.getenv() , as the environment is more often than not cached at virtual machine startup in a java.util.Map (or equivalent.)
   • To change the JVM’s cached copy of the environment, when a cache is used (see the source code in System.java in whichever JVM distribution you will be using to deploy), you may try hacking the implementation (via class loading order, reflection, or instrumentation.) In the case of SUN’s v1.6 JVM, for example, the environment cache is managed by the undocumented ProcessEnvironment class (which you can patch.)
2. Can we modify the environment of the parent process?
   • Extremely difficult, and highly non-portable. If you absolutely and imperatively have to, there are very specific hacks that you can employ:
     • Windows: Dynamically Add/Edit Environment variables of Remote process
     • *nix: Is there a way to change another process’s environment variables? — this is a performance killer, as any process instrumented by gdb will be suspended for a non-zero amount of time.
3. Can we modify the environment of the child process?
   • Yes, through ProcessBuilder when spawning the process.
   • If the process has already been spawned when the environment alteration is required, you need method 2 above (or some equally convoluted method, such as code-injection at spawn time, ulteriorly controlled through e.g. socket by the parent process.)

Note that all methods above, except for the one involving ProcessBuilder , are brittle, error prone, non-portable to various degrees, and prone to race conditions in multi-threaded environments.

How to set environment variable in java [duplicate]

I want to set environment variable in JAVA . For this , I have searched a lot in internet and got the following code .

But after execution , the envorinment variable is not set in «PATH» varaible . Why ?

2 Answers 2

Simple example for how to set path with setx.exe in command line:

try this on your code

A process can only set environment variables of itself and for processes it will spawn in future. A process cannot set the environment variables of already running processes.

You might have already noticed that when you were setting environment variables manually, globally in the system. They will not affect instances of processes which are already running, like an already running cmd.exe or an already running bash . You might also have noticed, that if you set an environment variable that way, that whether or not a new process gets the new environment variable setting depends on how the new process is started. The default behavior is that a process is started with a copy of the environment of its parent process, which is the process that starts the new process.

As a simple explanation, you could say there are root processes and child processes. root processes get the environment settings from the global settings, child processes inherit the environment settings from their parent processes.

The question is what do you want to achieve with setting the environment? I could think of at least three different things that you could want to achieve:

• Set the environment globally, as part of an installer.
• Set the environment for the currently running JVM.
• Set the environment for a process that you will be starting.
• Set the environment for the calling process directly (not possible!).
• Set the environment for the calling process indirectly.

Setting the environment globally, as part of an installer

This is highly system-specific. On UNIX, this topic is actually avoided. Programs would rather provide wrapper scripts that set the environment instead of setting global environment variables. The philosophy in UNIX is that usually environment variables are only used in cases where the variable would be useful for more than just one process. Examples for such varaibles are PATH and EDITOR .

On Windows, you would probably call regedit to modify the environment.

Setting the environment of the currently running JVM

There is no API for setting the environment of the currently running JVM, so you would have to use JNI for this. However, be advised, that the fact that there is no API for this is for good reasons, and part of these reasons might be that the JVM doesn’t want its environment be arbitrarily changed by some Java code.

Setting the environment for a process that will be started

When you start a process using one of the Runtime.exec() methods, you can actually provide the environment that you like.

If you want to start a process with a modified environment, the best way would be to use ProcessBuilder . It provides a method environment() for modifying the environment for the new process.

Setting the environment for the calling process directly

If you want to implement the set command in Java, forget it, it is not possible. set is not a program, it’s an internal command of the shell, i.e. cmd.exe . Because of the explanation above, it wouldn’t work otherwise.

Setting the environment for the calling process indirectly