Hello all!
I'm fairly new to processing and need some help with collision.
I am trying to figure out how to make the ball correctly bounce off of the paddle and the walls.
I have looked at the pong example game and it helps but I can't grasp how collisions work in programming.
Any help with my code or explaining how collisions work would be appreciated.
Sorry about the lack of objects but I tried to keep the code as clean as possible.
Any responses are appreciated.
Here's the code.

int paddleWidth;
int paddleHeight;
int paddleX;
int paddleY;
float paddleSpeed;

int ballRadius;
float ballX;
float ballY;
float dirX;
float dirY;


void setup () {
 size(640, 480);
 rectMode(CENTER);
 ellipseMode(CENTER);
 paddleWidth = 120;
 paddleHeight = 10;
 paddleX = width/2;
 paddleY = height - paddleHeight;
 paddleSpeed = 10;
 ballRadius = 10;
 ballX = width/2;
 ballY = -height + height - ballRadius;
 dirY = 1;
 dirX = 0;
}

void draw() {
  BackScreen();
  Paddle();
  Ball();
  BallMovement();
  PaddleControl();
  PaddleContain();
  Miss();
}

void BackScreen() {
  rectMode(CORNER);
  noStroke();
  fill(0);
  rect(0, 0, width, height);
}

void Paddle() {
  rectMode(CENTER);
  fill(255);
  noStroke();
  rect(paddleX, paddleY, paddleWidth, paddleHeight);
}

void Ball() {
  fill(255);
  noStroke();
  smooth();
  ellipse(ballX, ballY, ballRadius*2, ballRadius*2);
}

void BallMovement() {
  ballY += dirY * 5.0;
  ballX += dirX;
}

void BallBounce() {
  if(ballY < height - paddleHeight && ballX < paddleX + (paddleWidth/2)
  && ballX > paddleX - (paddleWidth/2)) {
    dirY *= -1;
  }
}

void PaddleControl() {
  if(keyPressed && paddleX + (paddleWidth/2) < width) {
    if(key == CODED) {
      if(keyCode == RIGHT) {
        paddleX += paddleSpeed;
      }
    }
  }
  if(keyPressed && paddleX - (paddleWidth/2) > width - width) {
    if(key == CODED) {
      if(keyCode == LEFT) {
        paddleX -= paddleSpeed;
      }
    }
  }
}

void PaddleContain() {
}

void Miss() {
  if(ballY > height) {
    ballY = height - height - (ballRadius*2);
  }
}