How to change the class of son's function which inherited from father class?

Sure, I can help you with that. Here's an implementation of the Employee class: ```java public class Employee extends Person { private double annualSalary; private int startYear; private String nationalInsuranceNumber; public Employee(String name, double annualSalary, int startYear, String nationalInsuranceNumber) { super(name); this.annualSalary = annualSalary; this.startYear = startYear; this.nationalInsuranceNumber = nationalInsuranceNumber; } public Employee(String name) { super(name); } public double getAnnualSalary() { return annualSalary; } public void setAnnualSalary(double annualSalary) { this.annualSalary = annualSalary; } public int getStartYear() { return startYear; } public void setStartYear(int startYear) { this.startYear = startYear; } public String getNationalInsuranceNumber() { return nationalInsuranceNumber; } public void setNationalInsuranceNumber(String nationalInsuranceNumber) { this.nationalInsuranceNumber = nationalInsuranceNumber; } public boolean equals(Employee other) { return super.equals(other) && this.annualSalary == other.annualSalary && this.startYear == other.startYear && this.nationalInsuranceNumber.equals(other.nationalInsuranceNumber); } } ``` In this implementation, the Employee class extends the Person class, which contains the name field. The Employee class then adds three additional fields: annualSalary, startYear, and nationalInsuranceNumber. The class contains two constructors - one that takes all four fields as arguments and another that only takes the name field. It also contains accessor and mutator methods for each of the fields. Finally, there is an equals method that compares two Employee objects for equality based on all four fields. Here's an example of how you might test this class: ```java public class EmployeeTest { public static void main(String[] args) { Employee employee1 = new Employee("John Doe", 50000, 2010, "123-45-6789"); Employee employee2 = new Employee("Jane Doe", 50000, 2010, "123-45-6789"); System.out.println(employee1.equals(employee2)); // true employee2.setStartYear(2011); System.out.println(employee1.equals(employee2)); // false } } ``` In this example, we create two Employee objects with the same salary, start year, and national insurance number, but different names. We then test the equals method to verify that it correctly identifies these objects as equal based on all four fields. We then modify the start year of employee2 and test the equals method again to verify that it correctly identifies these objects as unequal based on the start year field.

Here is the code for the HistoryPanel class: ```java import java.awt.Graphics; import java.util.ArrayList; import javax.swing.JPanel; public class HistoryPanel extends JPanel { private Library library; public HistoryPanel(Library library) { this.library = library; } private int historyMax(ArrayList<Integer> list) { int max = Integer.MIN_VALUE; for(int num : list) { if(num > max) { max = num; } } return max; } private int historyMin(ArrayList<Integer> list) { int min = Integer.MAX_VALUE; for(int num : list) { if(num < min) { min = num; } } return min; } private int historyRange(ArrayList<Integer> list) { int difference = historyMax(list) - historyMin(list); if(difference < 10) { return 10; } return difference; } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); ArrayList<Integer> history = library.getHistory(); int numPoints = history.size(); int maxValue = historyMax(history); int minValue = historyMin(history); int range = historyRange(history); int xSpacing = getWidth() / numPoints; int ySpacing = getHeight() / range; for(int i = 0; i < numPoints - 1; i++) { int x1 = i * xSpacing; int y1 = (history.get(i) - minValue) * ySpacing; int x2 = (i + 1) * xSpacing; int y2 = (history.get(i + 1) - minValue) * ySpacing; g.drawLine(x1, getHeight() - y1, x2, getHeight() - y2); } } } ``` In the constructor, we store the Library model object in a private instance variable. The three private methods `historyMax`, `historyMin`, and `historyRange` are used to calculate the maximum, minimum, and range of values in an arraylist of integers. In the `paintComponent` method, we first retrieve the history data from the Library object and calculate the maximum, minimum, and range of values. We then calculate the spacing between points for both the x and y axes. Finally, we loop through each point in the history and draw a line between it and the next point. Note that we use the `getHeight` method to adjust the y-coordinates of the points so that they are drawn from the bottom of the panel upwards. This is because the origin (0,0) of the coordinate system in Swing is at the top-left corner of the panel, whereas in most mathematical systems it is at the bottom-left corner.