../courses.php
Java
JAVA105
3
Objects Create Boundaries
Java uses classes and objects to keep responsibilities separated.
Why not put everything into one giant file?
One giant file becomes hard to read, test, repair, and trust. Objects create boundaries so each part of the program has a clear job.
Large programs become messy when everything is placed together.
Java encourages programmers to divide work into classes.
A class describes a kind of thing.
An object is a real instance of that class.
This gives the program boundaries, names, and responsibility.
A class with one clear responsibility
class Customer {
String name;
Customer(String name) {
this.name = name;
}
void printGreeting() {
System.out.println("Hello, " + name);
}
}
public class Main {
public static void main(String[] args) {
Customer customer = new Customer("Maya");
customer.printGreeting();
}
}
Customer is a class.
The class holds customer-related information.
new Customer("Maya") creates an object.
printGreeting() is behavior that belongs to the customer object.
The customer logic is not mixed into every part of the program.
Boundaries
Classes separate one responsibility from another.
Names
A class gives a concept a clear name.
Repair
Smaller parts are easier to fix.
Teams
Different people can work on different parts.
Everything in main
String customerName = "Maya";
System.out.println("Hello, " + customerName);
Customer class owns customer behavior
Customer customer = new Customer("Maya");
customer.printGreeting();
Ask ChatGPT: "Does this Java code put too much responsibility in one place, or should part of it become a class?"
Create a Customer class.
Give the class a name field.
Create a Customer object.
Call a method on the object.
Explain what boundary the class creates.
Putting all code in main forever.
Creating classes with unclear jobs.
Thinking objects are only advanced theory.
Mixing unrelated responsibilities.
Naming classes after vague ideas.
Explain how Java classes and objects create useful program boundaries.
Login - Jit4All
Login
Welcome back to Jit4All