Java Object: Meet Objects

Objects in Java are an extremely important concept. While you can continue on and see if you'll get it down, maybe a different explanation would help.

in Object-Oriented languages like Java, "classes" are used as a mold for creating variables with a specified set of properties and functions attached.

For example, say you're writing a program that needs to keep track of contact information, you may have a class that looks like the following:

public class Contact {
    // properties
    String firstName;
    String lastName;
    String phoneNumber;

    // constructor
    public Contact (String initialFirstNameValue, String initialLastNameValue, String initialPhoneNumberValue) {
        this.firstName = initialFirstNameValue;
        this.lastName = initialLastNameValue;
        this.phoneNumber = initialPhoneNumberValue
    }

    // methods
    public String getFirstName() {
        return this.firstName
    };

    public String setFirstName(String newFirstName) {
        this.firstName = newFirstName;
    };

    public String getLastName() {
        return this.lastName
    };

    public String setLastName(String newLastName) {
        this.lastName = newLastName;
    };

    public String getPhoneNumber() {
        return this.phoneNumber
    };

    public String setPhoneNumber(String newPhoneNumber) {
        this.phoneNumber = newPhoneNumber;
    };
}

The important parts here are the properties of the class, the constructor, and the methods.

In our example, each Contact would have a first name, last name, and phone number we could assign. The constructor would allow us to set initial values for those names, and then we have getter and setter functions to retrieve or change that information. Every time we declare a new Contact variable, we'd need to set those values, and then we can access them using the methods we created.

Objects are complex, and there's a lot of depth to them that you'll learn about, but pretend it's a contract you're making with the object to have the given properties and methods available to them, and they need whatever the constructor is to get started.