What are the path variable supposed to be to ensure "javac" will work? Should it be in both system and user variables and should the "\bin" part be included?
I have a Program Files and Program Files(x86) and the JDK is in both. Which one should i use? Eclipse is working perfectly, it's only when using command line that I get this. Anyone?
Eclipse comes with its own Java compiler, it doesn't have to use an external one.
You should find the bin directory under whichever JDK you want to use and then add it to the path (I prefer the user path but, since I only ever run as one user, I'm not sure what the difference is).
And make sure it's the JDK, not just the JRE.
For example, mine is in c:\program files\java\jdk1.6.0_17\bin (32-bit WinXP).
One final thing, if you're changing the environment variables in the control panel, that won't affect cmd windows that are already open. You'll need to open up a new one to get the new environment settings (trap for wary players).
Related
So I have been trying to run some of my school assignments, which are written in Java.
This is the only screenshot I can get, because every time I try to run it, the Java Console Launcher pops up and ask for permission, then no matter what I click, the program does not run. Although I can run it on VS Code for some reason, so I don't know what is the problem here.
I tried reinstalling Java with the aid of my instructor, but the problem persists.
When you type a command in the terminal it looks for the application using the operating systems PATH variable. The java installer (and most other programs for that matter) doesn't modify that variable, so you have to add it manually.
Find out where your java installation is, usually somewhere like C:\Program Files\Java\jdkXXX\bin
You can set the variable temporarily in your terminal like so:
set path=C:\Program Files\Java\jdkXXX\bin
and then verify if it works by typing java -version
If that all works, then you can modify your Windows PATH variable. There are lots of guides online for how to do that depending on your version of windows. Just make sure you append the jdk forlder instead of replacing the whole thing.
I'm trying to make Java work with some commands in a .bat file without installation. I have the Java folder that is installed in C:\Program Files when you normally install Java and Init.bat which does this:
set JAVA_HOME="C:\Users\mega\Desktop\DISK\Apps\Java"
set PATH=%PATH%;C:\Users\mega\Desktop\DISK\Apps\Java\bin
assoc .jar=jarfile
ftype jarfile="C:\Users\mega\Desktop\DISK\Apps\Java\bin\javaw.exe" "%1"
It should set the 2 environment variables and associating the variables, first of all, they don't set the variables, I do not know why but I am sure that I can fix it after this topic, but even then, I set them manually and when I try to open a .jar file it doesn't work.
So the Java is in 1 folder and it should function like if a Java were to be installed normally, but it doesn't, any help is good since I can't figure it out.
Why is there no need to add the path of the java installation to the PATH variable when starting a jar with double-click while it is needed to start the jar from command line? Why does the OS only know where java is installed when executing with a double-click (without the PATH variable)?
Related Questions:
Is it necessary to set the path variable in java installation?
Is JAVA_HOME variable needed when Java Path is defined in system environment variable?
When on the command line, you call an executable and pass it a file as an argument. Since it does not know where this executable is, you either need to call it with an absolute path (Includes the entire path from the drive letter to the executable) or the executable must be present in one of the locations listed in the system PATH environment variable.
However, when double clicking a file Windows does not have the luxury of being told which application it should use ahead of time. To solve this issue, Windows keeps a global registry of programs, file extensions, and various metadata about them. This includes stuff like which icon to display for that file type, the path to the executable used to open that file, extensions associated with a given program, the path to the uninstaller to use if deleted from the control panel, and much more.
The Java installer handles updating the registry for you behind the scenes so you don't need to, however depending on your installation setting it may not update the system path since most people will only use the double clicking method.
So I am trying to start with Java (as in, trying to get the dang thing to accept code). I download all the needed things (the SDK) from Java and such, but when it gets to the point where I have to do "javac" in Command Prompt to compile the notepad file, I just get the message saying that there is no command called "javac".
Anybody wanna share some insight?
To set the environment variable PATH: http://www.java.com/en/download/help/path.xml.
Also I recommend using an IDE such as netbeans or eclipse. They make it much easier when starting off in java, plus when getting into advanced projects with many classes, they help greatly.
You need to set the path to your java compiler for it to be found when you use the command prompt. This page explains how.
I would suggest setting the following environment variable:,
JAVA_HOME to point to the root of your java installation e.g. C:\Program Files\Java
than append the following to your PATH environment variable:
;%JAVA_HOME%\bin
than you will be able to use java and javac from the command line.
Also see this article from Microsoft on setting environment variables if your not familiar with it.
You need to add the Java bin directory (where javac.exe is located, assuming you're on Windows), to your system PATH.
Right click on "My Computer", go to Environment Variables, and add the bin directory where Java is installed to your PATH variable.
You will need to have the java bin directory on your path. So, on windows, if installed at c:\java, and bin is c:\java\bin (normally you have version number, jre vs sdk, etc), you will need to add that to your PATH environment variable. set PATH=c:\java\bin;%PATH% -- you could do this in a setlocal/endlocal block or set it permanatly for your machine.
Also, the JRE may not have javac -- you may need to dowload the SDK.
Starting with java by typing 'javac' at the command line satisfy my mother's definition of the phrase 'starting with' ... as in,
"Don't start with me, buddy."
You are likely to end up with a punch in the nose.
For your own sanity, pick one of Eclipse, or NetBeans, or IntelliJ, or the other popular IDEs, and start from there.
When I run it with NetBeans it's all OK. When I copy dist directory contents and run .jar, some stuff gets buggy. Most important, JTable editing gets messy, some fields lose focus only when you hit ESC (if you did hit ENTER before, changes are accepted, otherwise they are not, but you need ESC in both cases) and similar weird stuff. I got a feeling that I'm missing something obvious...
P.S. files are compiled automatically on save (NetBeans feature) if that matters.
Edit: when I just go to dist dir and run .jar, it works too. Problems begin when I copy dist dir out of NetBeans projects dir... can it be that some dependencies get broken or something?
Edit 2 (reply):
This problem was happening in my computer (Ubuntu 9.04), in my Windows XP inside Virtual Box and in another (real) computer with Windows XP. When I run it from console with java /path/to/main.jar it throws mainClassNot found exception and does not launch at all. When I run it with java -jar /path/to/main.jar, it works of sorts, but when it comes to said situations, it throws java.lang.NumberFormatException: null.
The only place I use NumberFormat (on table update) is:
DecimalFormat parser = new DecimalFormat("0.00");
And, possibly, this:
currencyFormatter = NumberFormat.getCurrencyInstance( Locale.getDefault() );
Where default locale is set to
Locale.setDefault(new Locale("lt", "LT"));
Java version is 1.6.0_18, both JDK used by NetBeans and JVM in said machines.
In NetBeans go to your project's properties (File > Project Properties). Go to the Libraries tab. Click Manage Platforms and see the value for the Platform Folder.
From a console, run <platform folder>\java -version.
Now try it again without the full path; just java -version.
I would expect these are returning different values.
The path used by the IDE comes from the platform definition which, by default, is created when NB is installed and never updated. The path used in the console is from the windows PATH environment variable. This is updated whenever Java is installed and will, over time, diverge from the path used by the IDE.
A good rule of thumb is when Java prompts that an update is available it's time to add a new Java Platform in NetBeans.
I usually keep several platforms around. At a minimum:
latest versions of 1.4.2, 1.5.0, 1.6.0, and an old version of 1.6.0 (currently u4, the version we recommended in our first product release).
Have you tried something as mundane as making a clean build to make sure all new changes and resources are copied to the dist library?
Interesting... JAR's are stored in ZIP format, so you could try comparing the JAR that you've compiled with Netbean's JAR (if you can find it) to see exactly what is different.
Different JRE versions? That would be my guess, looking at your symptoms.
There are different ways to do this, but you could get the complete details of both the processes (one launched by NetBeans and one without) using jconsole (jdk_dir/bin/jconsole.exe). This would give you the JRE, loaded jars, etc that you could then compare...
HTH...