.class won't open, what do I need to download?

[kieran white]

Basically I made a very simple program just to print out Hello world! I ran the Hello.java and I got the Hello.class file, when I now try to run this again from the command prompt and expect it to output "hello world!" it just pops up saying:

Windows cannot open this file
- select a file to open with
- find a program online

what can I do in order to run and execute this program?

Thanks - Kieran.

[Campbell Ritchie]

Welcome to the Ranch
What instruction are you using at the command line? You are supposed to write

java Hello

…or whatever your class is called.
We have a useful FAQ, which will probably answer all your questions about it.

[Paul Clapham]

Hi Kieran, welcome to the Ranch!

The short answer is, you don't do that. But the much longer (and more useful) answer is one of the pages right here: How to create your first Java program. Check it out, work your way through it, and ask any follow-up questions here.

[kieran white]

Thanks:)

I did Hello.java and the first time it made the Hello.class and when I do it again it just pops up asking you what program to run it with

[kieran white]

None of the links work:(

[Paul Clapham]

In what way do they not work?

[Campbell Ritchie]

Paul C and I both posted the same link, and it worked when I tried it a minute ago.
If you have a .class file, you must have installed Java™ correctly. What you are supposed to do is navigate to your directory where you saved your Java™ work. I recommend you create a folder as shown here. You only need the mkdir instruction once. You can give it any name you wish. You give these instructions in this order:-

mkdir java
cd java
javac Hello.java
java Hello

Obviously if you are already in the correct folder, you only need the two lines starting “javac”. If you have a .class file, you must have got the javac instruction to work already. It does no harm to run javac twice, however.

[kieran white]

the page just didn't open correctly on my phone.

I'm following the instructions and now when I type Javac it says it's not recognized as a internal or external command, the only way to prevent this is by putting C:\Java\jdk1.7.0_40\bin\javac rather then C:\Java\jdk1.7.0_40

[Jesper de Jong]

kieran white wrote:the page just didn't open correctly on my phone.

Then open the page on a computer, that makes it a lot easier to read than on a small phone screen.

kieran white wrote:I'm following the instructions and now when I type Javac it says it's not recognized as a internal or external command, the only way to prevent this is by putting C:\Java\jdk1.7.0_40\bin\javac rather then C:\Java\jdk1.7.0_40

To get rid of this problem, set the PATH variable as described in the JDK installation instructions.

[kieran white]

I have done that so my PATH variable reads C:\WINDOWS\system32;C:\WINDOWS;C:\Java\bin (C:\java\bin is the location when everything is)
however now when I type in Javac it says:
Error: Could not find or load main class com.sun.tools.javac.Main


When I actually get past this bit where do I save my programs, in a completely different file or the same one?

[Jesper de Jong]

kieran white wrote:however now when I type in Javac it says:
Error: Could not find or load main class com.sun.tools.javac.Main

That's a strange error, and indicates that something is wrong with your JDK installation. Did you accidentally remove some jar file from the JDK?

[kieran white]

I don't think so I followed the steps and it's not working

[Maneesh Godbole]

Please double check if you have tools.jar under your JDK (not JRE) installation directory and copy paste the path to tools.jar here
On my system its located at JDK_HOME/lib

[kieran white]

Maneesh Godbole wrote:Please double check if you have tools.jar under your JDK (not JRE) installation directory and copy paste the path to tools.jar here
On my system its located at JDK_HOME/lib

I can't find JDK in the file Java, I have bin, db, include, jre, lib and some copyright and read me things

[Jesper de Jong]

Try uninstalling the JDK and installing it again. It looks like something is wrong with your JDK installation.

[kieran white]

Unistalled it and re installed still the same though
Is there anything else which can fix it?:/

[Campbell Ritchie]

Where did you install it?
What happens when you give the following four instructions at a command line:-

echo %PATH%
echo %CLASSPATH%
java -version
javac -version

?

[kieran white]

Campbell Ritchie wrote:Where did you install it?
What happens when you give the following four instructions at a command line:-

echo %PATH%
echo %CLASSPATH%
java -version
javac -version

?

C:\Users\Kieran>echo %path%
C:\WINDOWS\system32;C:\WINDOWS;C:\Java\bin

C:\Users\Kieran>echo %classpath%
%classpath%

C:\Users\Kieran>java -version
java version "1.7.0_40"
Java(TM) SE Runtime Environment (build 1.7.0_40-b43)
Java HotSpot(TM) Client VM (build 24.0-b56, mixed mode, sharing)

C:\Users\Kieran>javac -version
Error: Could not find or load main class com.sun.tools.javac.Main

[Campbell Ritchie]

The only one which looks wrong is the last. Have you tried uninstalling and reinstalling Java?

[Campbell Ritchie]

…with a new download?

[kieran white]

I'll try again

[kieran white]

been playing around with it and I finally think it works thanks a lot guys

[Campbell Ritchie]

Well done