Resolving version conflict between java and javac on Ubuntu

Question

I have a problem with my compiled Java application on Ubuntu. It throws UnsupportedClassVersionError. I am compiling with a higher JDK version than the one that is configured in my PATH to run Java:

$ javac -version
javac 1.7.0_147

$ java -version
java version "1.6.0_23"
OpenJDK Runtime Environment (IcedTea6 1.11pre) (6b23~pre11-0ubuntu1.11.10.2)
OpenJDK Client VM (build 20.0-b11, mixed mode, sharing)

How can I resolve this?

you may prefer to ask this question on http://askubuntu.com/ Anyways, check what java packages are installed and if the jre v1.7 is also installed you may need to configure what version to use with "alternatives" — Grims, May 14 '12 at 14:21
Alternatively, try compiling with `-target 1.6` or `-source 1.6`. — Fred Foo, May 14 '12 at 14:23

score 29 · Answer 1 · edited Mar 04 '20 at 16:25

Type following command in terminal :

  sudo update-alternatives --config java

It will ask you for:

There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection      Path                                            Priority   Status

    0           /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      auto mode

    1           /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      manual mode

    2            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java  1051      manual mode


  Press enter to keep the current choice[*], or type selection number:

I enter 2 as I want to use java 1.7.0_21

This option worked for me on Ubuntu 18.04 – Mandar Pandit Feb 07 '21 at 09:31 — Mandar Pandit, Feb 07 '21 at 09:31

score 21 · Answer 2 · answered Jun 17 '15 at 06:58

You will also need to do:

sudo update-alternatives --config javac

Select the desired java compiler from the list provided. For example on Centos 5

There are 2 programs which provide 'javac'.
Selection    Command
-----------------------------------------------
1           /usr/lib/jvm/java-1.6.0-openjdk/bin/javac
*+ 2        /usr/lib/jvm/java-1.7.0-openjdk/bin/javac

thejartender · Accepted Answer · 2012-05-14T14:43:08.677

9

Run either of the following to locate where the location is of that

javac 1.7.0_147

being used as follows:

whereis javac

or

 locate javac

or

find javac

Then once you found the directory, symbolically and forcefully link the bin contents to /usr/bin:

sudo ln -f -s [put location here]/bin/* /usr/bin

edited May 14 '12 at 14:43

answered May 14 '12 at 14:36

thejartender

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I am having the same issue, but when I try this I get a new, different error: "too many levels of symbolic links" – Paul May 23 '16 at 23:17
2

-1, please do not attempt this answer. I think it should be unselected as the accepted answer. This will most likely cause you machine to irreversibly messed up by creating circular symlinks all over your /usr/bin directory that cannot be deleted! – Paul May 24 '16 at 01:36
@Paul This answer was directed at a person whose `javac` was *not* in `/usr/bin`. If `[put location here]/bin` turned out to be `/usr/bin` then the command becomes something completely ridiculous which you should have known - if you had tried to understand this solution instead of applying it blindly – May 24 '16 at 02:21
I suppose that is true. I didn't mean to offend, and I think the answer is still useful. But maybe my public stupidity will prevent someone else from making the same mistake. – Paul May 24 '16 at 02:28

score 3 · Answer 4 · answered May 14 '12 at 14:27

3

This is what you want Java and Ubuntu. I have the same config basically, but I am switching back and forth from Glassfish and Java7. Take a look and try setting up your Java env in a similar fashion

answered May 14 '12 at 14:27

apesa

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Gautam · Answer 5 · 2019-11-27T04:53:14.437

I have added and installed alternatives for Java and Javac with below steps it work for me :

Steps 1: Add the Java and Javac alternatives :

Command to add Javac:

sudo update-alternatives --install "/usr/bin/java" "java" "/opt/amazon-jdk-11/bin/java" 1

i.e : "/opt/amazon-jdk-11/bin/javac" this the new path of java

sudo update-alternatives --install "/usr/bin/javac" "javac" "/opt/amazon-jdk-11/bin/javac" 1

i.e : /opt/amazon-jdk-11/bin/javac is the new path of javac

Steps 2: Installed the Java and Javac alternatives :

sudo update-alternatives --config javac
sudo update-alternatives --config javac

Once you enter above command you will able to see screen like below you can select your number that you want to configure java.

I have selected " 1 "int the list as I wanted to installed "/opt/amazon-jdk-11/bin/java" as my javac.

Verify your Java alternative installation is successful or not with below commands :

which javac and which java you will able to see screen like below :

Resolving version conflict between java and javac on Ubuntu

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