Classes

new

new will create a new instance of the object

Constructors

public class Point {
	public int intX, intY;
 
	// Every time we "new", it will call this now.
	public Point (int intX, int intY) {
		// "this" refers to the object you're in. intX and intY by itself are the parameters
		this.intX = intX;
		this.intY = intY;
	}
	// This constructor has no arguments. If you call new() with no arguments, it will call this constructor instead
	public Point() {
		intX = 0;
		intY = 0;
	}
}

• You cannot have two constructors of the same signature
  • A signature is the number and type of parameters

this and super

super allows you to access items in the parent classes. this allows you to access items inside of the class you are writing in.

public class Circle {
 
	Circle() {
		// this is used to access another constructor in the same class 
		this(10,20);
	}
	
	Circle(int x, int y) {
		// this is used to refer to the instance variable inside of "Circle"
		this.x = x;
		this.y = y;
	}
	
	int x, y;
}

Public / private

We don’t always want our attributes to be changeable and instead be protected.

public class Point {
	private int intX;
}
 
// somewhere else, in another class
main() {
	Point pt = new();
	pt.intX = 10; // This will not be allowed because intX is private
}

Static

• If the method / field is associated with the object, then it shouldn’t be static
• If there is a thing you want every class to share a value between, it can be static.
  • For instance, the # of people could be static, but the individual properties of a person is not static.
• The X coord of a point cannot be static because each object will have a different value for it

Override

@Override isn't needed but it communicates that you're overriding a method

public class Point {
	int intX, intY;
	
	@Override
	public String toString() {
		return "x: " + intX + " y: " + intY;
	}
}

Objects vs Classes

An instance of a class creates objects, which can be manipulated and changed, unlike classes, which are the blueprint

Misc

• Objects are stored in the |stack (Idk if we need to remember this or not)