Cohesion example 1

00 Original.java

class Game {
    int ballX = 0;
    int ballY = 0;
    
    public void update() {
        ballX = ballX + 5;
        ballY = ballY + 5;
    }
}

01 Worse.java

class Ball {
    int x = 0;
    int y = 0;
}

class Game {
    Ball ball = new Ball();
    
    public void update() {
        ball.x = ball.x + 5;
        ball.y = ball.y + 5;
    }
}

02 Better.java

class Ball {
    int x = 0;
    int y = 0;
    
    public void move() {
        x = x + 5;
        y = y + 5;
    }
}

class Game {
    Ball ball = new Ball();
    
    public void update() {
        ball.move();
    }
}

03 Extension.java

class Ball {
    int x = 0;
    int y = 0;
    
    public void move() {
        x = x + 5;
        y = y + 5;
    }
}

class Game {
    Ball balls[] = { new Ball(), new Ball() };
    
    public void update() {
        ball[0].move();
        ball[1].move();
    }
}

04 Extension Worse.java

class Ball {
    int x = 0;
    int y = 0;
}

class Game {
    Ball balls[] = { new Ball(), new Ball() };
    
    public void update() {
        // update the first ball
        ball[0].x = ball[0].x + 5;
        ball[0].y = ball[0].y + 5;
        // update the second ball
        ball[1].x = ball[1].x + 5;
        ball[1].y = ball[1].y + 5;
    }
}