src/com.enterprise_name.project_name. Main.java (the main class)

src/com.enterprise_name.project_name.model.(here all model classes)

src/com.enterprise_name.project_name.view.(here all view classes, JFrame, Jdialog,etc)

src/com.enterprise_name.project_name.view.resources.(here all the files and images used in the views *note)

src/com.enterprise_name.project_name.controller.(here all controller classes)

lib/(here all the external libraries - dont forget add to build path)

*note if you need some resource file (xml, config file, etc) create a package .resources. in the specific place where do you need (model, controller, view)

The folder structure in the src directory or of the entire project in general? Project source directory is usually driven by the convention of the build tool you're using, like gradle. The folder structure in your src directory is building the package names for your classes. The goal here is to be consistent within an organization and unique so there is little chance of ambiguity when you bring in a lot of external libraries.

If you run javac without any arguments, help content gets printed

Usage: javac <options> <source files>
where possible options include:
  -g                         Generate all debugging info
  -g:none                    Generate no debugging info
  -g:{lines,vars,source}     Generate only some debugging info
  -nowarn                    Generate no warnings
  -verbose                   Output messages about what the compiler is doing
  -deprecation               Output source locations where deprecated APIs are used
  -classpath <path>          Specify where to find user class files and annotation processors
  -cp <path>                 Specify where to find user class files and annotation processors
  -sourcepath <path>         Specify where to find input source files
  -bootclasspath <path>      Override location of bootstrap class files
  -extdirs <dirs>            Override location of installed extensions
  -endorseddirs <dirs>       Override location of endorsed standards path
  -proc:{none,only}          Control whether annotation processing and/or compilation is done.
  -processor <class1>[,<class2>,<class3>...]Names of the annotation processors to run; bypasses default discovery process
  -processorpath <path>      Specify where to find annotation processors
  -d <directory>             Specify where to place generated class files
  -s <directory>             Specify where to place generated source files
  -implicit:{none,class}     Specify whether or not to generate class files for implicitly referenced files
  -encoding <encoding>       Specify character encoding used by source files
  -source <release>          Provide source compatibility with specified release
  -target <release>          Generate class files for specific VM version
  -version                   Version information
  -help                      Print a synopsis of standard options
  -Akey[=value]              Options to pass to annotation processors
  -X                         Print a synopsis of nonstandard options
  -J<flag>                   Pass <flag> directly to the runtime system

And -d says -d <directory> Specify where to place generated class files

Starting from Java 7, you can use the java.nio.file.Files & java.nio.file.Paths classes.

Path path = Paths.get("C:\\Images\\Background\\..\\Foreground\\Necklace\\..\\Earrings\\..\\Etc");

try {
    Files.createDirectories(path);
} catch (IOException e) {
    System.err.println("Cannot create directories - " + e);
}

This is a tricky solution (because I used only one path to go to the whole structure).

If you don't like tricky solutions, you can use 4 simple paths instead:

Path p1 = Paths.get("C:\\Images\\Background");
Path p2 = Paths.get("C:\\Images\\Foreground\\Necklace");
Path p3 = Paths.get("C:\\Images\\Foreground\\Earrings");
Path p4 = Paths.get("C:\\Images\\Foreground\\Etc");

and then call the createDirectories method for all of them:

Files.createDirectories(p1);
Files.createDirectories(p2);
Files.createDirectories(p3);
Files.createDirectories(p4);