The purpose of this exercise is to check your understanding of the Java input/output system.

Duration: 2 hours

In this exercise, you will implement "Vehicle Rental Agency" with support for storing and reading/writing entities from/to csv files. The class diagram of the Domain model is shown in the figure below:

You are also given a description of the following interfaces and classes:

• The CsvStorage interface provides two methods for reading/writing data from/to a csv file.

• The Mapper interface provides static methods for converting text to an object of each entity class and vice versa.

• The CsvStorageImpl class implements the CsvStorage interface.

• The Demo class demonstrates how to use the CsvStorageImpl class to read objects of the Client, Employee, Vehicle, and Order type; print them to the console; and write objects of the Order type to a file

Note: You must not modify the Demo class. Files with a description of objects of entity classes are located in the folder "src/test/resources/entity/"

First, proceed to the Domain model classes and implement their content.
Then, proceed to the CsvStorageImpl class and implement its content:

• public CsvStorageImpl()
  Initializes the configuration properties of a csv file with the default values

• public CsvStorageImpl(Map<String, String> props)
  Initializes the configuration properties of a csv file with the received values

• <T> List<T> read(InputStream source, Function<String[], T> mapper) throws IOException
  Returns the contents of the received file as a list of objects. The operation algorithm is as follows: It reads lines with data descriptions through the received source stream. Then, it splits each string into an array of String elements using valuesDelimiter. Then, it converts the resulting array into an object of the T type using the mapper parameter, a function that creates an object of the T type with field values taken from the given array.

• <T> void write(OutputStream dest, List<T> value, Function<T, String[]> mapper) throws IOException
  Writes the obtained list of objects to the specified dest stream. The operation algorithm is as follows: Each object of the T type is converted into an array of the String type using the mapper parameter. The elements of the array are then collected into a single string using valuesDelimiter to separate them. Then, the resulting string is written to a file. The mapper parameter is a function that converts an object of the T type into an array of the String type.

• Domain model classes must have the following:
  • A default constructor
  • A constructor that takes values to initialize all fields as parameters
  • Getters and setters for all fields
  • The equals(), hashCode(), and toString() methods

Note: In the future, it is expected that objects of these classes will be transferred over a network or stored in a file or database.

• The string representation of an object of these classes must follow the following convention:

  Class_name{field1_name=field_value, field2_name=field_value, …}
  

  • If a class inherits another class, it must include inherited fields before its own fields:

     Class_name{parent_class_fields,   own_fields}
    

  • String values must be surrounded by apostrophes. For example: text='value'
  • If a field is a collection or an array, its value must be surrounded by square brackets.
  • Fields must be ordered as denoted in the UML class diagram.
• The configuration properties stored in the CsvStorageImpl class are as follows:
  • String encoding
    The encoding used when reading the csv files must be a valid charset. The default value is "UTF-8"
  • String quoteCharacter
    The quote character is used for string data. The default value is '"'
  • String valuesDelimiter
    The column delimiter character is used when reading a csv file. The default value is ","
  • boolean headerLine
    If true, the first line is considered a header and must be ignored. The default value is "true"
• Converting string data to object field values has the following features:
  • Empty string must be converted to null for referenced types or to the default value for primitive types.
  • A quoted empty string "" must be converted to an empty string. It is guaranteed that quoted strings will not contain the quoteCharacter character.
  • A string representation of a value must be quoted if it contains the valuesDelimiter character.
  • A string representation of a date must be in the format "yyyy-mm-dd". It is guaranteed that a date will not contain time-related values.
• Converting object fields to strings has the following features:
  • A null must be converted to an empty string.
  • An empty string must be converted to a quoted empty string "".
• The write() method of the CsvStorageImp class never writes column headers.

Let class A have the following description:

class A {
    private int p = 10;
    protected int a = 1;
    protected String s = "a string";
    // ...
}

The string representation of the object will be as follows:

A{p=10, a=1, s='a string'}

Let class B be the inheritor of class A and have the following description:

class B extends A {
    private int b = 5;
    private String t = "a text";
    private char[] chars = {'a', 'b'};
    // ...
}

The string representation of the object will be as follows:

B{a=1, s='a string', b=5, t='a text', chars=[a, b]}

You may not use lambda expressions or streams.