setting JAVA HOME CLASSPATH in CentOS 6

Question

I have unpacked my jdk in  usr java    and I put CLASSPATH  PATH  JAVA HOME into  etc profile like below   export JAVA HOME  usr java jdk1 7 0 21 export PATH  PATH  JAVA HOME bin export CLASSPATH  JAVA HOME jre lib ext  JAVA HOME lib tools jar   And when I compile some java file in  usr java jdk1 0 7 21 bin    it works  But when I am doing same thing on other folder  it doesn t   It displays NoClassDefFoundError   So I have checked ClASSPATH  PATH  JAVA HOME via echo   It shows like below    root localhost a   echo  JAVA HOME  usr java jdk1 7 0 21  root localhost a   echo  PATH  usr lib64 qt-3 3 bin  usr local bin  usr bin  bin  usr local sbin  usr sbin  sbin  home guest bin  usr java jdk1 7 0 21 bin  usr java bin  usr java jdk1 7 0 21 bin  root localhost a   echo  CLASSPATH  usr java jdk1 7 0 21 jre lib ext  usr java jdk1 7 0 21 lib tools jar   I want to use java in console  What can I do fir this situation   Thanks in advance   PS  of couse I did source  etc profile                    The Errors what I m facing with                          when I command java A My class name is A    Error  Could not find or load main class A   case I command java -cp  home guest workspace AAA src a  A  Exception in thread  main  java lang NoClassDefFoundError  A  wrong name  a A      at java lang ClassLoader defineClass1 Native Method      at java lang ClassLoader defineClass ClassLoader java 791      at java security SecureClassLoader defineClass SecureClassLoader java 142      at java net URLClassLoader defineClass URLClassLoader java 449      at java net URLClassLoader access 100 URLClassLoader java 71      at java net URLClassLoader 1 run URLClassLoader java 361      at java net URLClassLoader 1 run URLClassLoader java 355      at java security AccessController doPrivileged Native Method      at java net URLClassLoader findClass URLClassLoader java 354      at java lang ClassLoader loadClass ClassLoader java 423      at sun misc Launcher AppClassLoader loadClass Launcher java 308      at java lang ClassLoader loadClass ClassLoader java 356      at sun launcher LauncherHelper checkAndLoadMain LauncherHelper java 482                         full content of my code                                       java part  path is  usr guest workspace AAA src a A java  package a   public class A       public static void main String   args            System out println  a  n               etc profile part  left part is default   export JAVA HOME  usr java jdk1 7 0 21 export PATH  PATH  JAVA HOME bin export CLASSPATH  JAVA HOME jre lib ext  JAVA HOME lib tools jar   other parts might be helpful to solve    which java prints   usr java bin   there s symbolic link  My jdk location is  usr java jdk1 7 0 21  inside of   bin every code works fine  I did not touch  root  bash profile  I just edited  etc profile    Thanks for such interest  even though it does not figured out  your help was great healing to me  D Thanks again

User · Answer

It seems that you dont have any problem with the environmental variables        Compile your file from src with       javac a A java  Then  run your program as       java a A

User · Answer

Instructions    Click on the Terminal icon in the desktop panel to open a terminal window and access the command prompt  Type the command which java to find the path to the Java executable file  Type the command su - to become the root user  Type the command vi  root  bash profile to open the system bash profile file in the Vi text editor  You can replace vi with your preferred text editor  Type export JAVA HOME  usr local java  at the bottom of the file  Replace  usr local java with the location found in step two  Save and close the bash profile file  Type the command exit to close the root session  Log out of the system and log back in  Type the command echo  JAVA HOME to ensure that the path was set correctly    set java home in centos

User · Answer

Do the following steps    sudo -s yum install java-1 8 0-openjdk-devel vi  bash profile    and add below line into  bash profile file and save the file       export   JAVA HOME  usr lib jvm java-1 8 0-openjdk-1 8 0 171-8 b10 el7 5 x86 64    Note - I am using CentOS7 as OS

User · Answer

Search here for centos jre install all users   The easiest way to set an environment variable in CentOS is to use export as in    gt  export JAVA HOME  usr java jdk 1 5 0 12    gt  export PATH  PATH  JAVA HOME   However  variables set in such a manner are transient i e  they will disappear the moment you exit the shell  Obviously this is not helpful when setting environment variables that need to persist even when the system reboots  In such cases  you need to set the variables within the system wide profile  In CentOS  I   m using v5 2   the folder  etc profile d  is the recommended place to add customizations to the system profile  For example  when installing the Sun JDK  you might need to set the JAVA HOME and JRE HOME environment variables  In this case  Create a new file called java sh  vim  etc profile d java sh   Within this file  initialize the necessary environment variables  export JRE HOME  usr java jdk1 5 0 12 jre export PATH  PATH  JRE HOME bin  export JAVA HOME  usr java jdk1 5 0 12 export JAVA PATH  JAVA HOME  export PATH  PATH  JAVA HOME bin   Now when you restart your machine  the environment variables within java sh will be automatically initialized  checkout  etc profile if you are curious how the files in  etc profile d  are loaded    PS  If you want to load the environment variables within java sh without having to restart the machine  you can use the source command as in     gt  source java sh

User · Answer

Providing javac is set up through  etc alternatives javac  you can add to your  bash profile   JAVA HOME   l   which javac    while     do nl   readlink   l         nl       break   l  nl   done   echo   cd   dirname  l       pwd    export JAVA HOME

User · Answer

I had to change  etc profile d java env sh  to point to the new path and then logout login

User · Answer

I created a folder named a in  home prasanth and copied your code to a file named A java  I compiled from  home prasanth as javac a A java and run javac a A  I got output as      a

[java] setting JAVA_HOME & CLASSPATH in CentOS 6

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