How do I run a Java program from the command line on Windows?

Question

How do I run a Java program from the command line on Windows?

Question

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)?

Elizabeth Turner

2017/04/10

Popular Answer

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 -
  1. 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
  2. Executable by Entry Point:
    - jar -cvfe TheJavaFile.jar <MainClass> TheJavaFile.class
To run the Jar File
```
java -jar TheJavaFile.jar
```

jkhosla

2015/10/15

Read less...

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

Harshad Holkar

2018/09/20

Complile a Java file to generate a class:

javac filename.java

Execute the generated class:

java filename

Paresh3489227

2018/09/20

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.

Eliza Helena

2016/04/03

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

monika

2017/05/23

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).

YakovK

2017/01/31

Nicholas Kadaeux · Accepted Answer · 11/2/2017 10:26:24 AM

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!