If your Main class is in a package called FileManagement, then try:

java -cp . FileManagement.Main

in the parent folder of the FileManagement folder.

If your Main class is not in a package (the default package) then cd to the FileManagement folder and try:

java -cp . Main

More info about the CLASSPATH and how the JRE find classes:

• How Classes are Found
• Setting the class path (Solaris/Linux)
• http://en.wikipedia.org/wiki/Classpath_(Java)

You can use java.lang.Runtime.exec to run simple code. This gives you back a Process and you can read its standard output directly without having to temporarily store the output on disk.

For example, here's a complete program that will showcase how to do it:

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class testprog {
    public static void main(String args[]) {
        String s;
        Process p;
        try {
            p = Runtime.getRuntime().exec("ls -aF");
            BufferedReader br = new BufferedReader(
                new InputStreamReader(p.getInputStream()));
            while ((s = br.readLine()) != null)
                System.out.println("line: " + s);
            p.waitFor();
            System.out.println ("exit: " + p.exitValue());
            p.destroy();
        } catch (Exception e) {}
    }
}

When compiled and run, it outputs:

line: ./
line: ../
line: .classpath*
line: .project*
line: bin/
line: src/
exit: 0

as expected.

You can also get the error stream for the process standard error, and output stream for the process standard input, confusingly enough. In this context, the input and output are reversed since it's input from the process to this one (i.e., the standard output of the process).

If you want to merge the process standard output and error from Java (as opposed to using 2>&1 in the actual command), you should look into ProcessBuilder.

To compile the file, open your terminal and type

javac filename.java

To run the generated class file, use

java filename

But to do this you need to have the Java JDK installed in your computer. You can install it with the instructions in How do I install Java?.

I imagine the easiest way would be to press the blue arrow at the top.

If it has to be command line though, try

Javac Main.java

To compile the source to byte code which will give you a Main.class file, then

Java Main

To run it. The oracle website has a quick guide here