Develop Reference

How do I run a java program I wrote on Intellij OUTSIDE of Intellij? [duplicate]

I'm trying to execute a Java program from the command line in Windows. Here is my code:
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class CopyFile
{
public static void main(String[] args)
{
InputStream inStream = null;
OutputStream outStream = null;
try
{
File afile = new File("input.txt");
File bfile = new File("inputCopy.txt");
inStream = new FileInputStream(afile);
outStream = new FileOutputStream(bfile);
byte[] buffer = new byte[1024];
int length;
// copy the file content in bytes
while ((length = inStream.read(buffer)) > 0)
{
outStream.write(buffer, 0, length);
}
inStream.close();
outStream.close();
System.out.println("File is copied successful!");
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
I'm not sure how to execute the program - any help? Is this possible on Windows? Why is it different than another environment (I thought JVM was write once, run anywhere)?

Source: javaindos.
Let's say your file is in C:\mywork\
Run Command Prompt
C:\> cd \mywork
This makes C:\mywork the current directory.
C:\mywork> dir
This displays the directory contents. You should see
filenamehere.java among the files.
C:\mywork> set path=%path%;C:\Program Files\Java\jdk1.5.0_09\bin
This tells the system where to find JDK programs.
C:\mywork> javac filenamehere.java
This runs javac.exe, the compiler. You should see nothing but the
next system prompt...
C:\mywork> dir
javac has created the filenamehere.class file. You should see
filenamehere.java and filenamehere.class among the files.
C:\mywork> java filenamehere
This runs the Java interpreter. You should then see your program
output.
If the system cannot find javac, check the set path command. If javac
runs but you get errors, check your Java text. If the program
compiles but you get an exception, check the spelling and
capitalization in the file name and the class name and the java
HelloWorld command. Java is case-sensitive!

To complete the answer :
The Java File
TheJavaFile.java
Compile the Java File to a *.class file
javac TheJavaFile.java
This will create a TheJavaFile.class file
Execution of the Java File
java TheJavaFile
Creation of an executable *.jar file
You've got two options here -
With an external manifest file :
Create the manifest file say - MANIFEST.mf
The MANIFEST file is nothing but an explicit entry of the Main Class
jar -cvfm TheJavaFile.jar MANIFEST.mf TheJavaFile.class
Executable by Entry Point:
jar -cvfe TheJavaFile.jar <MainClass> TheJavaFile.class
To run the Jar File
java -jar TheJavaFile.jar

Complile a Java file to generate a class:
javac filename.java
Execute the generated class:
java filename

In case your Java class is in some package. Suppose your Java class named ABC.java is present in com.hello.programs, then you need to run it with the package name.
Compile it in the usual way:
C:\SimpleJavaProject\src\com\hello\programs > javac ABC.java
But to run it, you need to give the package name and then your java class name:
C:\SimpleJavaProject\src > java com.hello.programs.ABC

Since Java 11, java command line tool has been able to run a single-file source-code directly. e.g.
java HelloWorld.java
This was an enhancement with JEP 330: https://openjdk.java.net/jeps/330
For the details of the usage and the limitations, see the manual of your Java implementation such as one provided by Oracle: https://docs.oracle.com/en/java/javase/11/tools/java.html

Assuming the file is called "CopyFile.java", do the following:
javac CopyFile.java
java -cp . CopyFile
The first line compiles the source code into executable byte code. The second line executes it, first adding the current directory to the class path (just in case).

It is easy. If you have saved your file as A.text first thing you should do is save it as A.java. Now it is a Java file.
Now you need to open cmd and set path to you A.java file before compile it. you can refer this for that.
Then you can compile your file using command
javac A.java
Then run it using
java A
So that is how you compile and run a java program in cmd.
You can also go through these material that is Java in depth lessons. Lot of things you need to understand in Java is covered there for beginners.

You can compile any java source using javac in command line ; eg, javac CopyFile.java.
To run : java CopyFile.
You can also compile all java files using javac *.java as long as they're in the same directory
If you're having an issue resulting with "could not find or load main class" you may not have
jre in your path. Have a look at this question:
Could not find or load main class

On Windows 7 I had to do the following:
quick way
Install JDK http://www.oracle.com/technetwork/java/javase/downloads
in windows, browse into "C:\Program Files\Java\jdk1.8.0_91\bin" (or wherever the latest version of JDK is installed), hold down shift and right click on a blank area within the window and do "open command window here" and this will give you a command line and access to all the BIN tools. "javac" is not by default in the windows system PATH environment variable.
Follow comments above about how to compile the file ("javac MyFile.java" then "java MyFile") https://stackoverflow.com/a/33149828/194872
long way
Install JDK http://www.oracle.com/technetwork/java/javase/downloads/index.html
After installing, in edits the Windows PATH environment variable and adds the following to the path C:\ProgramData\Oracle\Java\javapath. Within this folder are symbolic links to a handful of java executables but "javac" is NOT one of them so when trying to run "javac" from Windows command line it throws an error.
I edited the path: Control Panel -> System -> Advanced tab -> "Environment Variables..." button -> scroll down to "Path", highlight and edit -> replaced the "C:\ProgramData\Oracle\Java\javapath" with a direct path to the java BIN folder "C:\Program Files\Java\jdk1.8.0_91\bin".
This likely breaks when you upgrade your JDK installation but you have access to all the command line tools now.
Follow comments above about how to compile the file ("javac MyFile.java" then "java MyFile") https://stackoverflow.com/a/33149828/194872

STEP 1: FIRST OPEN THE COMMAND PROMPT WHERE YOUR FILE IS LOCATED. (right click while pressing shift)
STEP 2: THEN USE THE FOLLOWING COMMANDS TO EXECUTE.
(lets say the file and class name to be executed is named as Student.java)The example program is in the picture background.
javac Student.java
java Student

As of Java 9, the JDK includes jshell, a Java REPL.
Assuming the JDK 9+ bin directory is correctly added to your path, you will be able to simply:
Run jshell File.java — File.java being your file of course.
A prompt will open, allowing you to call the main method: jshell> File.main(null).
To close the prompt and end the JVM session, use /exit
Full documentation for JShell can be found here.

Now (with JDK 9 onwards), you can just use java to get that executed.
In order to execute "Hello.java" containing the main, one can use:
java Hello.java
You do not need to compile using separately using javac anymore.

You can actually run Java program as you would shell or python scripts without manually compile the Java file, as described in
JEP 330. That is available since JDK 11.
If you create a file testing, and put the following you should be able to run it as command testing. You need to make it executable in Linux and Mac OSX with chmod +x testing.
#!/usr/bin/env java --source 11
public class Test {
public static void main(String [] args) {
System.out.println("Hello world!");
System.exit(0);
}
}
You are not allowed to use the file extension .java in the previous example.
$ chmod +x testing
$ ./testing
Hello world!
$
But you can still execute if it is was name Test.java without the shebang "#!" prefix like this:
public class Test {
public static void main(String [] args) {
System.out.println("Hello again!");
System.exit(0);
}
}
Then execute the file Test.java with following command:
$ java Test.java
Hello again!
$
So this works as long as you have a new enough Java compiler in the path, check with java -version. More information in this blog.

What is the proper entry point, when compiling java to jar?

So, when I write my java file:
public class Program
{
public static void main(String[] args)
{
System.out.println("Serious business logic.");
}
}
Then in windows cmd, I compile this way:
javac Program.java
jar cfe Program.jar Program Program.class
java -jar Program.jar
It's fine, and the result is:
"Serious business logic."
When in Netbeans I create a Project, it adds this line:
package program;
And I can not compile in cmd, only inside the IDE.
I've tried manifest.txt, UTF8 encoding without BOM, plus linebreak at the and of file.
Manifest.txt:
Main-Class: program.Program
"jar cvfm Program.jar Manifest.txt Program.class"
and without manifest.txt, just in cmd program.Program
"jar cfe Program.jar program.Program Program.class"
When I tried to run:
java -jar Program.jar
it results in:
"Error: Could not find or load main class program.Program"
I've already checked the following websites:
http://www.skylit.com/javamethods/faqs/createjar.html
https://docs.oracle.com/javase/tutorial/deployment/jar/build.html
and haven't got any idea how to do. Could you please help me?
How do I compile with package keyword? What is the proper entry point?
Thanks!
(ps jre1.8.0_91 ; jdk1.8.0_66 should I use same 32 or 64 bit for both of jre and jdk?)

Make sure when you are compiling your program as a JAR, Program.class is inside of a folder called program. The package keyword that Netbeans has added at the beginning of your script is telling the executable that it is inside of a folder called program. If you are just adding the class file without making sure it is in the correct package (folder), it will not run properly because it does not know where to find it. Your command should be changed to:
jar cvfm Program.jar Manifest.txt program
where program is a folder containing Program.class. Your manifest may be left alone but also needs to be included with compilation.

adding JAR class path in UBUNTU

This is might be a common question but I am not able to add class path for a JAR file in UBUNTU. I have given below all the details I know:
java is located here:
the o/p of which java command is - /usr/bin/java
sudo vim /etc/bash.bashrc
export CLASSPATH=$CLASSPATH:/downloads/aws-java-sdk-1.3.24/lib/aws-java-sdk-1.3.24.jar
ps: downloads folder is directly under the root
sudo vim /etc/environment
CLASSPATH="/usr/lib/jvm/jdk1.7.0/lib: /downloads/aws-java-sdk-1.3.24/lib/aws-java-sdk-1.3.24.jar:"
As you can see, I have added the class path in bashrc and etc/environment... but still I am getting an error while trying to run the S3Sample.java which comes with awssdk for java.
when I compile the java file, I get the following errors:
ubuntu#domU-12-31-39-03-31-91:/downloads/aws-java-sdk-1.3.24/samples/AmazonS3$ javac S3Sample.java
S3Sample.java:25: error: package com.amazonaws does not exist
import com.amazonaws.AmazonClientException;
Now, I clearly understand that the JAR file is not added to the class path and so I am not getting the error. I've also tried javac with the class path option - but it does not work :(
PS: JAVA home is set correctly as other java programs work properly.

To set the classpath, it is in most cases better to use the the -cp or -classpath argument when calling javac and java. It gives you more flexibility to use different classpaths for different java applications.
With the -cp and -classpath arguments your classpath can contain multiple jars and multiple locations separated with a : (colon)
javac -cp ".:/somewhere/A.jar:/elsewhere/B.jar" MyClass.java
java -cp ".:/somewhere/A.jar:/elsewhere/B.jar" MyClass
The classpath entry in the example sets the classpath to contain the current working directory (.), and the two jar files A.jar and B.jar.
If you want to use the CLASSPATH environment variable you can do
export CLASSPATH=".:/somewhere/A.jar:/elsewhere/B.jar"
javac MyClass.java
java MyClass

How to run Java program in command prompt

I created a Java project to call a Web service.
It has one Main java file and another class file.
I have used some jar files for HTTP client.
In Eclipse it runs fine.
I need to run the Java program in command prompt by passing some arguments.
In command prompt I went to src folder containing main java and sub class java file and gave the following command
javac mainjava.java
I'm getting following error
mainjava.java:14: cannot find symbol
symbol : class SubClass
here SubClass is my another java class file used to call the web service.
How to run the program by passing arguments?

javac is the Java compiler. java is the JVM and what you use to execute a Java program. You do not execute .java files, they are just source files.
Presumably there is .jar somewhere (or a directory containing .class files) that is the product of building it in Eclipse:
java/src/com/mypackage/Main.java
java/classes/com/mypackage/Main.class
java/lib/mypackage.jar
From directory java execute:
java -cp lib/mypackage.jar Main arg1 arg2

A very general command prompt how to for java is
javac mainjava.java
java mainjava
You'll very often see people doing
javac *.java
java mainjava
As for the subclass problem that's probably occurring because a path is missing from your class path, the -c flag I believe is used to set that.

You can use javac *.java command to compile all you java sources. Also you should learn a little about classpath because it seems that you should set appropriate classpath for succesful compilation (because your IDE use some libraries for building WebService clients). Also I can recommend you to check wich command your IDE use to build your project.

All you need to do is:
Build the mainjava class using the class path if any (optional)
javac *.java [ -cp "wb.jar;"]
Create Manifest.txt file with content is:
Main-Class: mainjava
Package the jar file for mainjava class
jar cfm mainjava.jar Manifest.txt *.class
Then you can run this .jar file from cmd with class path (optional) and put arguments for it.
java [-cp "wb.jar;"] mainjava arg0 arg1
HTH.

javac only compiles the code. You need to use java command to run the code. The error is because your classpath doesn't contain the class Subclass iwhen you tried to compile it. you need to add them with the -cp variable in javac command
java -cp classpath-entries mainjava arg1 arg2 should run your code with 2 arguments

Problems compiling and running Java app with Bluecove (NoClassDefFoundError)

I have this app that uses bluetooth, so I need both, bluecove and bluecove-gpl packages, when I run it in NetBeans I have no problem at all, and works perfectly fine. But I still can't compile and run from the command line (Ubuntu 11.04).
I'm using this line for compilation:
$ javac -Xlint:unchecked -classpath bluecove-2.1.0.jar:bluecove-gpl-2.1.0.jar Client.java
And it doesn't return errors and it generates a .class file
Then I try to run the .class file like this:
java -classpath bluecove-2.1.0.jar:bluecove-gpl-2.1.0.jar Client
But it returns a NoClassDefFoundError.
Could not find the main class: SPPClient.
Why is this happening?

You probably need to add your current directory (or whatever directory your class files reside in) to the class path.
Try something like
java -classpath .:bluecove-2.1.0.jar:bluecove-gpl-2.1.0.jar Client
or
java -classpath bin:bluecove-2.1.0.jar:bluecove-gpl-2.1.0.jar Client

You need to have the main class definition in the manifest file:
Main-Class: classname