java command line tools (java, javac, jar)

javac used to compile source files (*.java)

javac [-options] files

java used to run a compiled code (*.class)

java [-options] class [args...]

jar used to archive files into JAR (*.jar)

jar {ctxui}[vfm0Me] [jar-file] [manifest-file] [entry-point] [-C dir] files

In practise:
Source for Hello.java

package com.blogspot.programmerutilities;

public class Hello {

 public static void main (String[] args){
  System.out.println("Hello World!");
 }
}

Location of the file:

\src\com\blogspot\programmerutilities\Hello.java

Directory structure:

-src
   -com
      -blogspot
         -programmerutilities
            -Hello.java
-build

Compile source file using javac (-d option points to a directory where compiled files will be placed)

javac -d build \src\com\blogspot\programmerutilities\Hello.java

After compilation a Hello.class file will be placed in \build directory (and subdirectories accordingly to the package name).

-src
   -com
      -blogspot
         -programmerutilities
            -Hello.java
-build
   -com
      -blogspot
         -programmerutilities
            -Hello.class

To start this application go to \build (the directory directly above the outer directory of the package) and run java tool with a full name of the class (package and class name without an extension)

cd build
java com.blogspot.programmerutilities.Hello
// Prints "Hello World!"

To create java archive (JAR) run jar tool with a name of new created archive (hello.jar) and the most outer directory of the package name (com)

jar -cf hello.jar com

After that in \build directory the hello.jar file will be placed

-src
   -com
      -blogspot
         -programmerutilities
            -Hello.java
-build
   -com
      -blogspot
         -programmerutilities
            -Hello.class
   -hello.jar

To check the content of the jar run jar tool with -tf options (table of content and file name)

jar -tf hello.jar

To start an application using a jar file run java tool with -cp (or -classpath) option with a path to a jar and full name of a class

java -cp /build/hello.jar com.blogspot.programmerutilities.Hello
// Prints "Hello World!"