Where can I find the Java SDK in Linux after installing it?
I installed JDK using apt-get install but I don’t know where my jdk folder is. I need to set the path for that. Does any one have a clue on the location?
14 Answers 14
This depends a bit from your package system . if the java command works, you can type readlink -f $(which java) to find the location of the java command. On the OpenSUSE system I’m on now it returns /usr/lib64/jvm/java-1.6.0-openjdk-1.6.0/jre/bin/java (but this is not a system which uses apt-get ).
On Ubuntu, it looks like it is in /usr/lib/jvm/java-6-openjdk/ for OpenJDK, and in some other subdirectory of /usr/lib/jvm/ for Suns JDK (and other implementations as well, I think).
For any given package you can determine what files it installs and where it installs them by querying dpkg. For example for the package ‘openjdk-6-jdk’: dpkg -L openjdk-6-jdk
I think readlink as given is most elegant (and efficient), but I suggest readlink -f $(which javac) — note the ‘c’ in case there is a strange mix of JDK and JRE on the same machine. The JDK includes a compiler (javac) and a JRE does not. However if path is not correct, which will fail and you can try this: find /usr/java -wholename ‘*ava/jdk*’ -prune as I note in a comment below.
will tell you which java implementation is the default for your system and where in the filesystem it is installed. Check the manual for more options.
@dequis, it’s an answer specific to debian, since the question mentioned apt-get and the distro to be Debian 2.6.26 . AFAIK, it should be the same for all debian derivatives.
should give you something like
This does not actually point to a full JDK. 1. It is a symlink, and even if you read the symlink, the binary is also not within a JDK. For example, if I run the command readlink -f $(which javac) it prints /usr/lib/jvm/java-8-oracle/bin/javac . That bin folder is NOT a JDK. General acid-base test to see if its a JDK is to see if the current $JAVA_HOME contains a path of lib/tools.jar . In the cast of /usr/lib/jvm/java-8-oracle/bin that is not true, therefore it is not a JDK.
On Centos / RHL This is what I prefer to find the JDK (if installed) find /usr/java -wholename ‘*ava/jdk*’ -prune But behavior depends whether you are talking about OpenJDK or Oracle Java and how it was installed in the first place.
This question will get moved but you can do the following
«find / -name ‘javac'» is less typing, but requires admin (root) privilege or you will get a lot permission denied messages.
Use find to located it. It should be under /usr somewhere:
When running the command, if there are too many «Permission denied» message obfuscating the actual found results then, simply redirect stderr to /dev/null
find /usr -name java 2> /dev/null Another best way to find Java folder path is to use alternatives command in Fedora Linux (I know its for Ubuntu but I hit this post from google just by its headline). Just want to share incase people like me looking for answers for fedora flavour.
To display all information regarding java
alternatives --display java Three Step Process: First: open Terminal-> $ whereis java it would give output like this: java: /usr/bin/java /usr/share/java /usr/share/man/man1/java.1.gz
Second: ls -l /usr/bin/java It would give output like this: lrwxrwxrwx 1 root root 22 Feb 9 10:59 /usr/bin/java -> /etc/alternatives/java
Third: ls -l /etc/alternatives/java output is the JDK path: lrwxrwxrwx 1 root root 46 Feb 9 10:59 /etc/alternatives/java -> /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
It’s /usr/local/java/jdk[version]
This question still seems relevant, and the answer seems to be a moving target.
On my debian system (buster):
> update-java-alternatives -l java-1.11.0-openjdk-amd64 1111 /usr/lib/jvm/java-1.11.0-openjdk-amd64 However, if you actually go look there, you’ll see there are multiple directories and symbolic links placed there by the package system to simplify future maintenance.
The actual directory is java-11-openjdk-amd64 , with another symlink of default-java . There is also an openjdk-11 directory, but it appears to only contain a source.zip file.
Given this, for Debian ONLY, I would guess the best value to use is /usr/lib/jvm/default-java , as this should always be valid, even if you decide to install a totally different version of java, or even switch vendors.
The normal reason to want to know the path is because some application wants it, and you probably don’t want that app to break because you did an upgrade that changed version numbers.
PATH and CLASSPATH
This section explains how to use the PATH and CLASSPATH environment variables on Microsoft Windows, Solaris, and Linux. Consult the installation instructions included with your installation of the Java Development Kit (JDK) software bundle for current information.
After installing the software, the JDK directory will have the structure shown below.
The bin directory contains both the compiler and the launcher.
Update the PATH Environment Variable (Microsoft Windows)
You can run Java applications just fine without setting the PATH environment variable. Or, you can optionally set it as a convenience.
Set the PATH environment variable if you want to be able to conveniently run the executables ( javac.exe , java.exe , javadoc.exe , and so on) from any directory without having to type the full path of the command. If you do not set the PATH variable, you need to specify the full path to the executable every time you run it, such as:
C:\Java\jdk1.7.0\bin\javac MyClass.java
The PATH environment variable is a series of directories separated by semicolons ( ; ). Microsoft Windows looks for programs in the PATH directories in order, from left to right. You should have only one bin directory for the JDK in the path at a time (those following the first are ignored), so if one is already present, you can update that particular entry.
The following is an example of a PATH environment variable:
C:\Java\jdk1.7.0\bin;C:\Windows\System32\;C:\Windows\;C:\Windows\System32\Wbem
It is useful to set the PATH environment variable permanently so it will persist after rebooting. To make a permanent change to the PATH variable, use the System icon in the Control Panel. The precise procedure varies depending on the version of Windows:
- Select Start, select Control Panel. double click System, and select the Advanced tab.
- Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New .
- In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
- From the desktop, right click the My Computer icon.
- Choose Properties from the context menu.
- Click the Advanced tab (Advanced system settings link in Vista).
- Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New .
- In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
- From the desktop, right click the Computer icon.
- Choose Properties from the context menu.
- Click the Advanced system settings link.
- Click Environment Variables. In the section System Variables, find the PATH environment variable and select it. Click Edit. If the PATH environment variable does not exist, click New .
- In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
Note: You may see a PATH environment variable similar to the following when editing it from the Control Panel:
%JAVA_HOME%\bin;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem
Variables enclosed in percentage signs ( % ) are existing environment variables. If one of these variables is listed in the Environment Variables window from the Control Panel (such as JAVA_HOME ), then you can edit its value. If it does not appear, then it is a special environment variable that the operating system has defined. For example, SystemRoot is the location of the Microsoft Windows system folder. To obtain the value of a environment variable, enter the following at a command prompt. (This example obtains the value of the SystemRoot environment variable):
Update the PATH Variable (Solaris and Linux)
You can run the JDK just fine without setting the PATH variable, or you can optionally set it as a convenience. However, you should set the path variable if you want to be able to run the executables ( javac , java , javadoc , and so on) from any directory without having to type the full path of the command. If you do not set the PATH variable, you need to specify the full path to the executable every time you run it, such as:
% /usr/local/jdk1.7.0/bin/javac MyClass.java
To find out if the path is properly set, execute:
This will print the version of the java tool, if it can find it. If the version is old or you get the error java: Command not found, then the path is not properly set.
To set the path permanently, set the path in your startup file.
For C shell ( csh ), edit the startup file (~/.cshrc ):
set path=(/usr/local/jdk1.7.0/bin $path)
For bash , edit the startup file ( ~/.bashrc ):
PATH=/usr/local/jdk1.7.0/bin:$PATH export PATH
For ksh , the startup file is named by the environment variable, ENV . To set the path:
PATH=/usr/local/jdk1.7.0/bin:$PATH export PATH
For sh , edit the profile file ( ~/.profile ):
PATH=/usr/local/jdk1.7.0/bin:$PATH export PATH
Then load the startup file and verify that the path is set by repeating the java command:
% source ~/.cshrc % java -version
Checking the CLASSPATH variable (All platforms)
The CLASSPATH variable is one way to tell applications, including the JDK tools, where to look for user classes. (Classes that are part of the JRE, JDK platform, and extensions should be defined through other means, such as the bootstrap class path or the extensions directory.)
The preferred way to specify the class path is by using the -cp command line switch. This allows the CLASSPATH to be set individually for each application without affecting other applications. Setting the CLASSPATH can be tricky and should be performed with care.
The default value of the class path is «.», meaning that only the current directory is searched. Specifying either the CLASSPATH variable or the -cp command line switch overrides this value.
To check whether CLASSPATH is set on Microsoft Windows NT/2000/XP, execute the following:
On Solaris or Linux, execute the following:
If CLASSPATH is not set you will get a CLASSPATH: Undefined variable error (Solaris or Linux) or simply %CLASSPATH% (Microsoft Windows NT/2000/XP).
To modify the CLASSPATH , use the same procedure you used for the PATH variable.
Class path wildcards allow you to include an entire directory of .jar files in the class path without explicitly naming them individually. For more information, including an explanation of class path wildcards, and a detailed description on how to clean up the CLASSPATH environment variable, see the Setting the Class Path technical note.
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