我有不同版本的javac和java。 我正在尝试在终端上运行.java文件。 但是它可以在日食中工作

Question

How to resolve this? I can compile it but I can't run it. I have different versions of javac and java . I'm trying to run my .java file on terminal. But it works in eclipse. I know that version affects this. How to upgrade javac ? Will it affect my eclipse if I do so? Thanks. ;)

[clemjon@localhost ~]$ javac -version

javac 1.6.0_20


[clemjon@localhost ~]$ java -version

java version "1.6.0_21"

Java(TM) SE Runtime Environment (build 1.6.0_21-b06) Java HotSpot(TM) Server VM (build 17.0-b16, mixed mode)

Answer 1

Check which JRE eclipse is using:

Window->Preferences->Java->JREs Right click the selected one and Edit .
The JRE home path should be there. Add that path to your path environment variable (instead of the one that is already there) and that should do the trick for you.

You can also set which JDK version you want Eclipse to compile to:
Window->Preferences->Java->Compiler

My best advice would be to keep track of all the installed JDK's and JRE's.

Choose the ones you want to use by default and add those to your JAVA_HOME and Path environment variables; Then setup your Eclipse to the same values using the steps above.

Then if for a particular project you need to use a specific JRE, right click on that project and then go to BuildPath -> Libraries -> JRE Library -> Edit and pick you JRE.

Disclaimer: I'm not on my dev machine right now so the names may be approximate. :)

Answer 2

This is not an issue to do with different versions of javac and java . The problem here is that you are attempting to run a class file whose fully-qualified name ( com.pl.casestudy.First ) doesn't match the class name you passed to java ( First ). You would get the same error if you had the same versions of javac and java .

If you have a class whose name is com.pl.casestudy.First , Java will look for it in a file with name com/pl/casestudy/First.class (Windows users feel free to reverse the direction of the slashes.) So you will need to run your First class from the directory that contains the com subdirectory. I can see from the shell prompt in your stacktrace that you have a directory named casestudy , I'll assume that the com and pl parent directories also exist. Eclipse has probably created them for you.

Try cd ing out to the directory that contains com , compiling using

javac com/pl/casestudy/First.java

and running using

java com.pl.casestudy.First