Java Hello • 9 min read

public class Student { //Class, where the code is run (a template for creating objects structure and behavior of objects)
    public static void main(String[] args) { //Main method, where the code is executed and calls other functions
        Student student1 = new Student("Alice", 20); //Create object using Student constructor

        student1.introduce();
        student1.changeName("Bobert");
        student1.introduce();
    }

    public String name; //instance variables
    public int age;

    public Student(String name, int age) //Student constructor with 2 parameters
    {
        this.name = name;
        this.age = age;
    }

    public void changeName(String newName) //Setter that changes the name of the student
    {
        this.name = newName;
    }

    public void introduce() { //Function/Method that prints the name and age of the person
        System.out.println("Hello, my name is " + getName() + " and I am " + getAge() + " years old.");
    }

    public String getName() {//Getter for name
        return name;
    }

    // Getter for age
    public int getAge() {
        return age;
    }
}
public class Teacher {
    public static void main(String[] args) {
        Teacher teacher1 = new Teacher("Mr. Bortenson", "A999");
        teacher1.introduceTeacher();
    }

    public String teachername;
    public String classroom;

    // Constructor for the Teacher class
    public Teacher(String name, String classroom)  //Teacher constructor with 2 parameters
    { 
        this.teachername = name;
        this.classroom = classroom;
    }

    public void introduceTeacher() {
        System.out.println("Hello, my teacher's name is " + teachername + " and they are in classroom " + classroom + ".");
    }
}
Student.main(null);
Teacher.main(null);

Hello, my name is Alice and I am 20 years old.
Hello, my name is Bobert and I am 20 years old.


Hello, my teacher's name is Mr. Bortenson and they are in classroom A999.

Explaining Static vs Dynamic

You cannot create objects of a static class, which differs from a dynamic one.

The following code demonstrates a series of static classes.

Date functions using static

import java.util.*;
import java.time.*;


public class DateUtils {
    // Calculate age since a given date
    public static void calculateAge(LocalDate birthDate, LocalDate currentDate) {        
        System.out.println(Period.between(birthDate, currentDate).getYears());
}

    // Calculate the older of two dates
    public static void findOlderDate(LocalDate date1, LocalDate date2) {
        if (date1.isBefore(date2)) {
            System.out.println(date1);
        }
        else
        {
            System.out.println(date2);
        }
    }

    // Calculate the number of time since a given date
    public static void calculateSecondsSince(LocalDate startDate) {
        LocalDate now = LocalDate.now();
        Period period = Period.between(startDate, now);
        System.out.println(period);
    }
    public static void main(String[] args) 
    {
        LocalDate birthDate = LocalDate.parse("2006-09-08");
        LocalDate currentDate = LocalDate.now();
        calculateAge(birthDate, currentDate);

        LocalDate date1 = LocalDate.parse("2006-09-08");
        LocalDate date2 = LocalDate.parse("2006-09-09");
        findOlderDate(date1, date2);

        LocalDate startDate = LocalDate.parse("2006-09-08");
        calculateSecondsSince(startDate);
    }
}
DateUtils.main(null);

16
2006-09-08
P16Y11M24D

Statistic functions using static

import java.util.Arrays;

public class StatsUtils {
    // Calculate the mean
    public static void calculateMean(int[] values) {
        int sum = 0;
        for (int i= 0; i < values.length; i++) {
            sum += values[i];
        }
        System.out.println(sum / values.length);
    }

    // Calculate the median
    public static void calculateMedian(int[] values) {
        Arrays.sort(values);
        int middle = values.length / 2;
        System.out.println(values[middle]);
    }

    // Calculate the mode
    // public static int calculateMode(int[] values) {
    //     Map<Integer, Integer> valueFrequency = new HashMap<>();
    //     int mode = -1;
    //     int maxFrequency = 0;

    //     for (int i = 0; i < values.length; i++) {
    //         int frequency = valueFrequency.getOrDefault(value, 0) + 1;
    //         valueFrequency.put(value, frequency);

    //         if (frequency > maxFrequency) {
    //             mode = value;
    //             maxFrequency = frequency;
    //         }
    //     }

    //     System.out.println(mode);
    // }

    public static void main(String[] args) {
        int[] values = {42, 18, 7, 56, 91, 32, 5, 67, 23, 10};

        calculateMean(values);
        calculateMedian(values);
        // calculateMode(values);
    }
}
StatsUtils.main(null);

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