gravity in java

const GRAVITY = 10;
const TERMINAL_VELOCITY = 300;

object Player 
{
    int vertical_speed = 0;
    int vertical_position;  

    function fall ()
    {
        this.vertical_speed = this.vertical_speed + GRAVITY;
        if (this.vertical_speed > TERMINAL_VELOCITY)
        {
            this.vertical_speed = TERMINAL_VELOCITY;
        }
        this.vertical_position = this.vertical_position - this.vertical_speed;
    }
}    GRAVITY = 10;
    TERMINAL_VELOCITY = 300;
    vertical_speed = 0;

    public void fall(){ 
    this.vertical_speed = this.vertical_speed + GRAVITY;
    if(this.vertical_speed > TERMINAL_VELOCITY){
        this.vertical_speed = TERMINAL_VELOCITY;
    }
    this.y = this.y - this.vertical_speed;
}