OOP Java Array Tutorial

Product.java

public class Product {
    public static void main(String[] args) {
        calculate(1);
        calculate(1, 2);
        calculate(1, 2, 3);
        calculate(1, 2, 3, 4);
    }
    public static void calculate(int ... i) {
        int sum = 0;

        System.out.printf("Number of arguments: %d", i.length);

        for (int j : i) {
            sum += j;
        }
        System.out.printf(", Sum: %d%n", sum);
    }
}

TestTeacher.java

public class TestTeacher {
    public static void main(String[] args) {
        Teacher teachers[] = new Teacher[10];

        teachers[0] = new Teacher("Shigetora", 72.7);
        teachers[1] = new Teacher("Teacher 1", 10);
        teachers[2] = new Teacher("Teacher 2", 20);
        teachers[3] = new Teacher("Teacher 3", 30);
        teachers[4] = new Teacher("Teacher 4", 40);
        teachers[5] = new Teacher("Teacher 5", 50);
        teachers[6] = new Teacher("Teacher 6", 60);
        teachers[7] = new Teacher("Teacher 7", 70);
        teachers[8] = new Teacher("Teacher 8", 80);
        teachers[9] = new Teacher("Teacher 9", 90);
        
	for (Teacher teacher : teachers) {
            displaySalary(teacher);
        }
        // displaySalary(teachers[0]);
    }
    public static void displaySalary(Teacher teacher) {
        System.out.printf("Name: \t\t%s%n" +
                          "Hours Worked: \t%.2f%n" +
                          "Salary: \t%.2f%n", teacher.getName(), teacher.getHoursWorked(), teacher.computePay());
        System.out.printf("%n");
    }
}
public class Teacher {
    private String name;
    private double hoursWorked;
    static final int RATE = 30;

    public Teacher() {

    }
	public Teacher(String name, double hoursWorked) {
		this.name = name;
        this.hoursWorked = hoursWorked;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public double getHoursWorked() {
		return hoursWorked;
	}
	public void setHoursWorked(double hoursWorked) {
		this.hoursWorked = hoursWorked;
	}
    public double computePay() {
        return (hoursWorked*RATE);
    }
}