Sand Man Enemy (Greenfoot)

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * An enemy which is stationary on the ground, but is periodicly jumping up, from the ground
 * and then is going down again.
 *
 * @author Martin Rohwedder
 * @version 1.0
 */
public class SandMan extends Enemy
{
    //Constants defining the minimum and maxiumum y position this enemy can 'jump' to.
    private final int MAX_Y_POS = 695;
    private final int MIN_Y_POS = 645;

    private int speed = 3;

    private boolean doJumpAnimation = false;
    private boolean stretching = false;
    private int timeCycle = 120;

    /**
     * Act - do whatever the SandMan wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act()
    {
        checkForOnGoingAnimation();
        doJumpAnimation();
    }

    /**
     * Check if the animation is in action or not. If not the time cycle will be resetted, and
     * the animation can begin again.
     */
    private void checkForOnGoingAnimation()
    {
        //If not doing jump animation, then go ahead and do it.
        if(!doJumpAnimation)
        {
            if (timeCycle <= 0)
            {
                doJumpAnimation = true;
                if (doJumpAnimation)
                {
                    //Reset Time cycle to between 1 and 4 seconds.
                    timeCycle = Greenfoot.getRandomNumber(240) + 60;
                }
            }
            else
            {
                //Decrement time by 1
                timeCycle--;
            }
        }
    }

    /**
     * Do the actual jump animation. If the enemy is stretching (it's at its highest), then
     * make the animation, so the enemy go down, and otherwise up.
     */
    private void doJumpAnimation()
    {
        if (doJumpAnimation)
        {
            //If stretching, make the enemy animate downwards
            if (stretching)
            {
                if (getY() < MAX_Y_POS)
                {
                    setLocation(getX(), getY() + speed );
                }
                else
                {
                    stretching = false;
                    doJumpAnimation = false;
                }
            }
            else
            {
                if (getY() > MIN_Y_POS)
                {
                    setLocation(getX(), getY() - speed );
                }
                else
                {
                    stretching = true;
                    doJumpAnimation = false;
                }
            }
        }
    }
}