I'm new in programming, I'm learning Java right now. I tried to use the javac command, but the environment says that javac is an unknown command.
How to use "javac" to compile .java files from the command prompt? I'm using eclipse 1.2.2.20100216-1730, JRE 1.6 and JRE6
The JRE has the "java" program for running programs already compiled. The "javac" program is only in the JDK. Download and install the JDK. If BTW it still gives you the same error, then you need to add the javac directory to your PATH environment variable.
Before the Java virtual machine (VM) can run a Java program, the program's Java source code must be compiled into byte-code using the javac compiler. Java byte-code is a platform independent version of machine code; the target machine is the Java VM rather than the underlying architecture. To compile a Java source code file add.java, you would do the following:
javac add.java
If there are no errors in your source file, the Java compiler will produce one or more .class files (one .class file for each class defined in the add.java source file). For example, the results of a successful compile of Foo.java will produce a byte-code version of the class in a file named Foo.class.
Every public class that you write must be in a separate .java file where the first part of the file name is identical to the class name. The .java file additionally can contain code for protected and private classes.
Once you have successfully compiled your Java source code, you can invoke the Java VM to run your application's byte-code:
java <class with main method to run> [<command line args>, ...]
For example, to run the main method from the Foo class:
java Foo
Any command line arguments (arguments to add's main method) follow the class name:
java add 10 20
Such Error may occur due to two reasons:
You have not installed java jdk on your system.
You have not set the environment variables.classpath ,path.
Setting Path and classPath:
Windows XP
Select Start, select Control Panel. double click System, and select the Advanced tab.
Click Environment Variables. In the section System Variables, find the PATH environment variable and select it.
Click Edit. If the PATH environment variable does not exist, click New.
In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
Windows Vista:
From the desktop, right click the My Computer icon.
Choose Properties from the context menu.
Click the Advanced tab (Advanced system settings link in Vista).
Click Environment Variables. In the section System Variables, find the PATH environment variable and select it.
Click Edit. If the PATH environment variable does not exist, click New.
In the Edit System Variable (or New System Variable) window, specify the value of the PATH environment variable. Click OK. Close all remaining windows by clicking OK.
If you have not set the classpath and path you can access javac giving full path:
such as C:\Java\jdk1.7.0\bin\javac MyClass.java
To check the path and classpath, type these commands in a command window:
echo $PATH
echo $CLASSPATH
If you get a blank command line in response to either of these, then that particular variable has no value (it has not yet been set).
setting path and classpath through cmd:
set path=c:\j2sdk1.4.1_01\bin(Give the path of bin)
set classpath=;(or the directory where you want your class files)
Download and install JDK
set environment path --> edit path in environment path and add ;/bin
using javac command --> javac *.java or javac ClassName.java
When run the main method you should note to [package] name
java packagename.ClassName
Related
I have the JDK 10.0.2 installed, have the cmd opened in the folder of the class files of my program and try the command: javap Simulation.class .
I get the error that the command javap is not found. What do I do wrong?
You must have your $JAVA_HOME/bin directory added to system PATH for javap command to be available without it's absolute path.
Alternatively you can call javap using the absolute path:
/usr/lib/.../bin/javap Simulation.class
Assuming you are on Windows, check in your environment variable PATH whether path to Java executables is set.
Ex. If you have installed Java on path,say, C:\Program Files\Java\jdk-10
Then you have to add C:\Program Files\Java\jdk-10\bin to your PATH environment variable to be able to execute java commands from anywhere on command line.
References for Oracle Docs
https://docs.oracle.com/javase/10/install/installation-jdk-and-jre-microsoft-windows-platforms.htm#JSJIG-GUID-DAF345BA-B3E7-4CF2-B87A-B6662D691840
https://www.java.com/en/download/help/path.xml
On a sidenote, recommend you to move to Java 11 or 17 now that Java 10 is no longer supported. The above instructions would still remain same.
append $JAVA_HOME/bin to system $PATH variable. for example on linux
JAVA_HOME= "path of java installation on system"
export PATH = $JAVA_HOME/bin:$PATH
Open the control panel and type envir in search bar.
Click on edit the system environment variables.
Click on environment variables in the advanced system properties.
Click on path mentioned in user variables.
Edit the path, and click new and paste the path of java jdk.
In my system, the path is C:\Program Files\Java\jdk-17.0.2\bin, it could be different for your system.
Click ok, the problem must be solved now.
When I go to open eclipse, it gives me a run time error saying that the path to the JDK is not right.
I have no idea where to save the link so that i can get it to open
First Install Java on your pc: It should create Java Folder in C:\Program Files.
You have to set Classpath like this :
Set the CLASSPATH environment variable
(for **Windows NT/2000/XP**)
1. At the left bottom corner of your computer desktop, choose Start -> Setting -> Control Panel, and double-click System
2. On Microsoft Windows NT, select the Environment tab; on Microsoft Windows
2000/XP select the Advanced tab and then Environment Variables.
3. For either User variables or System variables, click New and in the popup window, enter Variable name as CLASSPATH (note that all letters should be capital), and the directory where your JDK is installed as the Variable value.
For example:
If your JDK is installed at: C:\jdk1.4.1_06
Put the following line as the value:
C:\jdk1.4.1_06\bin;C:\jdk1.4.1_06\jre\bin;.
The first is where the java compiler 'javac' is, the second is the java run time environment 'java' is, and the final '.' denotes your working directory, so that the compiler and jre will find where your programs are. To be safe, you may also want to append the above line to then end of your PATH variable. Use ';' as the separator.
Save the variables, test the setting by opening a DOS prompt, type in
echo %CLASSPATH%
If your environment variables are set correctly, you should see your settings.
Or, you can just type in
javac
java
If your PATH and CLASSPATH is correct, windows should recognize those commands.
You do NOT need to restart your computer when installing Java.
Check whether TextPad and Java SDK work on your computer
Download HelloWorld.java into your local drive. Be sure that filename is case sensetive in JAVA programming.
Start TextPad, and open this HelloWorld.java file.
Click menu "Tools" ---> "Compile Java" to compile java file.
Click menu "Tools" ---> "Run Java Application" to run this file.
If you see "Hello World" in a DOS PROMPT window, that means there is no problem with your TextPad to compile/run Java program. Congratulations. You can start your java programming now. If you see some errors when run Java program, please click here to get more information.
For a more comprehensive description on how to setup Java environment on Windows machinese, please refer to the Sun document at: http://java.sun.com/j2se/1.4.2/install-windows.html
For **windows 7**: Follow this link http://www.abodeqa.com/2012/08/11/how-to-set-path/
Then : Start Compatible eclipse (e.g :64bit eclipse on 64bit os).
In Eclipse, select Windows | Preferences
Click the + in front of Java or double-click Java (after the +)
Click Installed JREs
Under the Name column, double-click jre1.5.0_08.
Click the Add External Jars... button.
In the Jar Selection window, navigate to your workspace folder, and double-click the file cs15-1xx.library.
In the Edit JRE window, click OK
In the Installed JREs window, click OK
Terminate (X) the Welcome window
You can always get it back by selecting Help | Welcome
Terminate (X) the Eclipse window.
For more Details follow this : http://blog.ajduke.in/2013/04/28/setting-up-new-java-compiler-and-runtime-in-eclipse-ide/
You can specify the target JRE when launching eclipse by with the -vm command line argument (either through a shortcut or in the eclipse.ini file).
Command line syntax: eclipse -vm c:\jre\bin\javaw.exe
eclipse.ini file syntax (use 2 lines)
-vm
c:/jre/bin/javaw.exe
You can also copy a given version of the JRE under your eclipse installation directory.
Generally speaking I would really advise against adding %JAVA_HOME%/bin to your SYSTEM path. In my experience, this usually leads to many unexpected behaviors. Far better IMHO to set the JAVA_HOME and add its /bin directory to the PATH through scripts/command line/shortcuts/etc. and invoke those when needed.
I have to convert my Matlab algorithm in Java. For this I'm using matlab builder ja toolbox, after following all the necessary steps, the build fails and this error is displayed:
'javac' is not recognized as an internal or external command, operable program or batch file. Error: An error occurred while shelling out to javac (error code = 1). Unable to build executable.
When typing java -version in the matlab command line, this is what i get:
Java 1.6.0_12-b04 with Sun Microsystems Inc. Java HotSpot(TM) Client VM mixed mode
It means I should have this compiler of java installed on my computer, only then the matlab builder ja works. I'm new to Java, I'm not sure what compiler I should be looking for.
First make sure you have installed jdk and jre, both are installed with the java software development kit. The installation folder is typically C:\Program Files\Java.
Now go to Computer > Properties > Advanced system settings in the advanced tab click on Environment Variables
In System variables find the variable named Path, in the value of Path you will find a java path like C:\ProgramData\Oracle\Java\javapath, just change it to C:\Program Files\Java\jdk1.x.x_x\bin.
Hope that helps.
If you want javac (the compiler), you'll need to download the Java Development Kit (JDK), not just the Java Runtime Environment (JRE). Note that the JDK includes a JRE.
This tutorial give instructions to install JDK to your computer.
You need to make sure that Java SDK is installed and also PATH is set properly so that windows would be able to know where the executable is. Detailed steps on how to debug this issue is explained here: http://www.windows-commandline.com/javac-not-recognized-internal-external-command/
To solve the aforementioned problem follow the mentioned steps:
1) Copy the address location of your Java\jdk\bin folder usually installed in your C: drive. It should look something like this:
C:\Program Files (x86)\Java\jdk1.8.0_65\bin
2) Right click on My Computer-->Properties-->Change settings-->
Advanced-->Environment Variables.. -->New..
3) Now,
Set Variable name: PATH
Variable value: C:\Program Files (x86)\Java\jdk1.8.0_65\bin
4) Press OK, re-open your cmd and compile your program.
Hopefully it worked!
Path is defined as the filename. Ex, C://aklsej;dlfkj/blahblah
You will need to specify the full path in the system control panel, advanced system settings, edit variables, edit path, put a semicolon after the last entry and don't delete anything, and then add the full path wherever you installed java to.
to make this easy, do a search for javac in the search panel and then just add the full path to the environmental variables from there.
Set Following Environment Variables
It will works
JAVA_HOME=C:\Program Files\Java\jdk1.7.0_09
set PATH=%JAVA_HOME%\bin
Download Java from given link according to your requirements.
http://www.oracle.com/technetwork/java/javase/downloads/index.html
then follow below steps:
Step-1 : Right Click on MyComputer and click on properties .
Step 2 : Click on Advanced tab
Step 3 : Click on Environment Variables
Step 4 : Create a new class path for JAVA_HOME
Step 5 : Enter the Variable name as JAVA_HOME and the value to your jdk bin path ie c:\Programfiles\Java\jdk-1.6\bin and
NOTE Make sure u start with .; in the Value so that it doesn't corrupt the other environment variables which is already set.
Step 6 : Follow the Above step and edit the Path in System Variables add the following ;c:\Programfiles\Java\jdk-1.6\bin in the value column.
Step 7 :Your are done setting up your environment variables for your Java , In order to test it go to command prompt and type
java
who will get a list of help doc
In order make sure whether compiler is setup Type in cmd
javac
who will get a list related to javac
Hope this Helps !
If you receive this error, Windows cannot find the compiler (javac).
Here's one way to tell Windows where to find javac. Suppose you installed the JDK in C:\jdk1.8.0. At the prompt you would type the following command and press Enter:
C:\jdk1.8.0\bin\javac HelloWorld.java
If you choose this option, you'll have to precede your javac and java commands with C:\jdk1.8.0\bin\ each time you compile or run a program. To avoid this extra typing, consult the lecture "Creating a Hello World application" in this website
Class names, 'HelloWorld', are only accepted if annotation processing is explicitly requested
If you receive this error, you forgot to include the .java suffix when compiling the program. Remember, the command is javac HelloWorld.java not javac HelloWorld.
I have done a lot of researching on this concept but I can't seem to run a java program on the command prompt. Let's say we had a simple program like this:
public class Hello_World {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
On the command prompt I tried:
javac Hello_World.java
But I get:
'javac' is not recognized as an internal or external command, operable program or batch file
So I compiled it on BlueJ and then did this:
java Hello_World.java
But it said "cannot load or find main class Hello_World"!
I am currently using Windows 7, and made the programs on Notepad++ and BlueJ (to compile).
Any suggestions? Thanks!
This explains in detail what you have to do to set class path. Primarily you need to set your environment variables so that your shell finds the right directory containing javac to compile your program
javac' is not recognized ..
comes when you haven't point your java bin directory to your path environment variable. Because bin directory is the place where javac.exe exist.
To do it.
1) right click on mycomputer property
2) go to Advance system settings.
3) go to environment variable.
4) In system variable click on path
5) go to edit mode and provide your path to java bin directory.
in my case it is C:\Program Files\Java\jdk1.7.0_01\bin;
'javac' is not recognized as an internal...
means OS does not know where javac program is located. Either add it to PATH or run explicitly
my\path\to\file\javac Hello_World.java
Compiling will convert *.java to *.class
Hello_World.class file should be located according to it's package directive. Since you have no one, in your case it should be located in the same directory you will run java.
To run your class specify it's name not file name
java Hello_world
looking for the class is essential part of launching and occurs by rules.
Here's the address on my drive:
C:\Program Files\Java\jdk1.6.0_18\bin
How would I go about setting the path variable so I can go in command window (windowskey+r "cmd") and be able to type things like:
javac TestApp.java
I'm using Windows 7 Professional.
That would be:
set "PATH=%PATH%;C:\Program Files\Java\jdk1.6.0_18\bin"
You can also append ;C:\Program Files\Java\jdk1.6.0_18\bin to the PATH in the user environment dialog. That would allow you to use javac and other java tools directly form any cmd shell without setting the path first. The user environment dialog used to be somewhere in the system properties in XP, I have no idea where it is in Windows 7.
Typing the SET PATH command into the command shell every time you fire it up could get old for you pretty fast. Three alternatives:
Run javac from a batch (.CMD) file. Then you can just put the SET PATH into that file before your javac execution. Or you could do without the SET PATH if you simply code the explicit path to javac.exe
Set your enhanced, improved PATH in the "environment variables" configuration of your system.
In the long run you'll want to automate your Java compiling with Ant. But that will require yet another extension to PATH first, which brings us back to (1) and (2).
Step 1: Set the PATH variable JAVA_HOME to the path of the JDK present on the system.
Step 2: in the Path variable add the path of the C:\Program Files\Java\jdk(version)\bin
This should solve the problem.
Happy coding!!
Type cmd in program start
Copy and Paste following on dos prompt
set PATH="%PATH%;C:\Program Files\Java\jdk1.6.0_18\bin"
Follow the steps given here
http://www.javaandme.com/
after setting variable, just navigate to your java file directory in your cmd and type
javac "xyx.java"
or if you don't navigate to the directory, then simply specify the full path of java file
javac "/xyz.java"
First thing I wann ans to this imp question: "Why we require PATH To be set?"
Answer : You need to set PATH to compile Java source code, create JAVA CLASS FILES and allow Operating System to load classes at runtime.
Now you will understand why after setting "javac" you can manually compile by just saying
"Class_name.java"
Modify the PATH of Windows Environmental Variable by appending the location till bin directory where all exe file(for eg. java,javac) are present.
Example : ;C:\Program Files\Java\jre7\bin.
only this will work:
path=%set path%;C:\Program Files\Java\jdk1.7.0_04\bin
You don't need to do any complex command-line stuff or edit any system code.
You simply have to open Computer, showing all of your disks and open properties.
From there, go to Advanced System Settings and click Environment Variables.
Scroll down in the lower list box and edit Path.
Do not erase anything already there. Put a ; after it and then type in your path. To test, open command prompt and do "javac", it should list around 20 programs.
You would be finished at that point.
By the way, the command to compile is javac -g not just javac.
Happy coding!
Trying this out on Windows 10, none of the command-line instructions worked.
Right clicking on "Computer" then open Properties etc. as the post by Galen Nare above already explains, leads you to a window where you need to click on "new" and then paste the path (as said: without deleting anything else). Afterwards you can check by typing java -version in the command-line window, which should display your current java version, if everything worked out right.