For all files and paths, use the Files and Paths APIs from the java.nio.file package when possible.

B The following private fields:

$1$ A static constant path for the base directories, which are db sub tables relative to the project directory.

$2$ A path for the table root, which is a directory containing a hierarchy of directories and files.

$3$ A path for the data directory, which is data resolved under the table root.

$4$ A path for the metadata directory, which is metadata resolved under the table root.

$5$ No fields for the degree, size, fingerprint, or other fields $($unlike in previous modules$),$ nor any other fields.

C A $2-$ary constructor which takes a name parameter $($string$)$ and a columns parameter $($list of strings$).$

$1$ Initialize the table root field by resolving the given name $($without an extension$)$ relative to the base directories.

$2$ Create the table root directory, if needed.

$3$ Initialize the data and metadata directories by resolving them under the table root.

$4$ Create the data and metadata directories, if needed.

$5$ Write the given columns as a list of lines $($strings$)$ to a columns file under the metadata directory.

D A $1-$ary constructor which takes a name parameter $($string$)$ only.

$1$ Initialize the table root field by resolving the given name $($without an extension$)$ relative to the base directories.

$2$ If the directory doesn$$t exist at the table root field, throw an illegal argument exception.

$3$ Initialize the data and metadata directories by resolving them under the table root.

E A private static writeInt method which takes a path parameter, then an integer parameter.

$1$ Use the Serializable API to write the given integer to the file at the given path using the default behavior.

$2$ This step E is the functional inverse of step F below.

F A private static readInt method which takes a path parameter and returns an integer.

$1$ Use the Serializable API to read the stored integer from the file at the given path using the default behavior.

$2$ Return the stored integer read from the file.

$3$ This step F is the functional inverse of step E above.

G In the Row record, modify the following features:

$1$ Mark that the record implements the Serializable interface, but don$$t implement any methods of that API.

H A private static writeRow method which takes a path parameter, then a row parameter.

$1$ Create the parent directories of the given path $($not the path itself, but the path$$s parent$),$ if needed.

$2$ Use the Serializable API to write the given row to the file at the given path using the default behavior.

$3$ This step H is the functional inverse of step I below.

I A private static readRow method which takes a path parameter and returns a row.

$1$ Use the Serializable API to read the stored row from the file at the given path using the default behavior.

$2$ Return the stored row read from the file.

$3$ This step I is the functional inverse of step H above.

J A private static deleteRow method which takes a path parameter.

$1$ Delete the file at the given path.

$2$ If the count of the list of files under the parent directory of the given path is now $0,$ delete the parent directory too.

K A private digestFunction method which takes a key parameter.

$1$ Define a salt which is a string literal containing your full name, then concatenate the salt with the given key.

$2$ Compute a digest from the salted key above using the MessageDigest algorithm SHA$-1($known to be compromised$).$

$3$ Use java.util.HexFormat to convert the digest bytes to a lowercase hexadecimal string of $40$ characters.

$4$ Return the hexadecimal string.

L A private pathOf method which takes a digest parameter $($hexadecimal string$).$

$1$ Find the $2-$character hexadecimal prefix and the $38-$character hexadecimal suffix of the digest.

$2$ Resolve the suffix file under the prefix directory under the data directory.

$3$ Return the resolved path, which is the data directory sub $2-$character prefix directory sub $38-$character suffix file.

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$2$ND QUARTER: FRAMEWORK, PUT, GET, REMOVE

M A public clear method.

$1$ Walk the data directory by streaming as follows:

i Skip the first path in the stream, which is itself being walked and shouldn$$t be deleted.

ii Sort the stream in reverse order, which streams from the lowest files to the highest directories.

iii For each path in the stream, delete the corresponding file or directory.

$2$ Call writeInt $0$ to the size file under the metadata directory.

$3$ Call writeInt $0$ to the fingerprint file under the metadata directory.

N Public methods for the following statistics and predicates:

$1$ The name method which returns the name of the table root, excluding the base directories $($without an extension$).$

$2$ The columns method which returns the lines $($list of strings$)$ read from the columns file under the metadata directory.

$3$ The degree method which returns the size of the list of columns which is returned by the columns method.

$4$ The size method which returns readInt from the size file under the metadata directory.