A class is a specification or blueprint from which individual objects are created. A class contains fields that represent the object’s states and methods that defines the operations that are possible on the objects of the class.

The file name that contains the definition of a class is always the same as the public class name and the extension is .java to identify that the file contains a Java source code.

A class has constructors, a special method that is used to create an instance or object of the class. When no constructor define a default constructor will be used. The constructor method have the same name with the class name without a return value. The constructors can have parameters that will be used to initialize object’s states.

Here is a Person.java file that defines the Person class.

package org.kodejava.example.fundamental;

public class Person {
    private String name;
    private String title;
    private String address;

    /**
     * Constructor to create Person object
     */
    public Person() {

    }

    /**
     * Constructor with parameter
     *
     * @param name
     */
    public Person(String name) {
        this.name = name;
    }

    /**
     * Method to get the name of person
     *
     * @return name
     */
    public String getName() {
        return name;
    }

    /**
     * Method to set the name of person
     *
     * @param name
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * Method to get the title of person
     *
     * @return title
     */
    public String getTitle() {
        return title;
    }

    /**
     * Method to set the title of person
     *
     * @param title
     */
    public void setTitle(String title) {
        this.title = title;
    }

    /**
     * Method to get address of person
     *
     * @return address
     */
    public String getAddress() {
        return address;
    }

    /**
     * Method to set the address of person
     *
     * @param address
     */
    public void setAddress(String address) {
        this.address = address;
    }

    /**
     * Method to get name with title of person
     *
     * @return nameTitle
     */
    public String getNameWithTitle() {
        String nameTitle;
        if (title != null) {
            nameTitle = name + ", " + title;
        } else {
            nameTitle = name;
        }
        return nameTitle;
    }

    /**
     * Method used to print the information of person
     */
    @Override
    public String toString() {
        return "Info [" +
                "name='" + name + ''' +
                ", title='" + title + ''' +
                ", address='" + address + ''' +
                ']';
    }
}

Here is a ClassExample.java file that defines the ClassExample class that use the Person class.

package org.kodejava.example.fundamental;

public class ClassExample {
    public static void main(String[] args) {
        Person person = new Person();
        person.setName("Andy");
        person.setTitle("MBA");
        person.setAddress("NY City");
        System.out.println(person);

        String nameTitle1 = person.getNameWithTitle();
        System.out.println("Name with title: " + nameTitle1);

        Person person2 = new Person("Sarah");
        String nameTitle2 = person2.getNameWithTitle();
        System.out.println("Name with title 2: " + nameTitle2);
    }
}