Stop Spawn Timer

public class MarioWorld extends World
{
    private GreenfootSound Music = new GreenfootSound("bgmusic.mp3");
    private GreenfootSound bossMusic = new GreenfootSound("bossfight.mp3");
    private int spawnTimer_;
    ScoreBoard board = new ScoreBoard();
    Lives lives = new Lives();
    HealthBar bar = new HealthBar();
    /**
     * Constructor for objects of class MarioWorld.
     * 
     */
    public MarioWorld()
    {    
        // Create a new world with 1000x680 cells with a cell size of 1x1 pixels.
        super(1000, 680, 1); 
        
        Mario hero = new Mario();
        addObject(hero, getWidth()/2, getHeight()/2);
        
        Lakitu player = new Lakitu(0.005);
        addObject(player, 26, 35);
        
        addObject(board, 876, 36);
        
        addObject(lives, 92, 647);
        
        spawnTimer_ = 0;
    }

    /**
     * @return ScoreBoard
     */
    public ScoreBoard getBoard()
    {
        return board;
    }
    
    /**
     * @return Lives
     */
    public Lives getLives()
    {
        return lives;
    }
    
    /** 
     * @return HealthBar
     */
    public HealthBar getBar()
    {
        return bar;
    }
    
    /**
     * Plays the music when the game is running.
     */
    public void started()
    {
        Music.playLoop();
    }
    
    /**
     * Stops the music when the game is stopped.
     */
    public void stopped()
    {
        Music.stop();
        bossMusic.stop();
    }
    
    public void act()
    {
        if(spawnTimer_ == 0) // same concept as reloadTimer_
        {
            spawnCheepCheep();
            spawnGreenCC();
        }
        else
        {
            spawnTimer_ --;
        }
        
        spawnBoss();
    }

    /**
     * Spawns the boss when Mario has collected 20 coins.
     * Adds in the health bar when Mario has collected 20 coins.
     * Starts the new music, and ends the old one.
     */
    public void spawnBoss()
    {
        if(Mario.coinsCollected_ >= 20)
        {
            addObject(bar, 552, 127);
            addObject(new Boss(), 1000, 340);
            bossMusic.playLoop(); //starts the new music 
            Music.stop(); //stops the original music to play bossfight music   
        }
    }
    
    /**
     * Spawns the amount of CheepCheep depending on the amount of coins Mario has collected.
     * Difficulty increases(more CheepCheep spawned) when Mario collectes 15 or more coins.
     */
    public void spawnCheepCheep()
    {
        //if Mario collects less than 15 coins, spawn 2 CC each time
        if(Mario.coinsCollected_ < 15)
        {
            CheepCheep enemy = new CheepCheep();
            CheepCheep enemy2 = new CheepCheep();
            addObject(enemy, 0, Greenfoot.getRandomNumber(496)+92);
            addObject(enemy2, 0, Greenfoot.getRandomNumber(496)+92);
            spawnTimer_ = 250;
        }
        //if Mario collects 15 or more coins, start spawning an extra CC
        //difficulty increases!
        else if(Mario.coinsCollected_ >= 15)
        {
            CheepCheep enemy = new CheepCheep();
            CheepCheep enemy2 = new CheepCheep();
            CheepCheep enemy3 = new CheepCheep();
            addObject(enemy, 0, Greenfoot.getRandomNumber(496)+92);
            addObject(enemy2, 0, Greenfoot.getRandomNumber(496)+92);
            addObject(enemy3, 0, Greenfoot.getRandomNumber(496)+92);
            spawnTimer_ = 300;
        }
    }
    
    /**
     * Spawns the amount of GreenCC depending on the amount of coins Mario has collected.
     * Difficulty increases as Mario collected 15 or more coins.
     */
    public void spawnGreenCC()
    {
        // if Mario has less than 15 coins collected spawnn 2 CC at once
        if(Mario.coinsCollected_ < 15)
        {
            GreenCC enemy3 = new GreenCC();
            GreenCC enemy4 = new GreenCC();
            addObject(enemy3, 1000, Greenfoot.getRandomNumber(496)+92);
            addObject(enemy4, 1000, Greenfoot.getRandomNumber(496)+92);
            spawnTimer_ = 200;
        }
        //if Mario collects 15 or more coins, then the number of CC spawns increases by 1
        else if(Mario.coinsCollected_ >= 15) 
        {
            GreenCC enemy3 = new GreenCC();
            GreenCC enemy4 = new GreenCC();
            GreenCC enemy5 = new GreenCC();
            addObject(enemy3, 1000, Greenfoot.getRandomNumber(496)+92);
            addObject(enemy4, 1000, Greenfoot.getRandomNumber(496)+92);
            addObject(enemy5, 1000, Greenfoot.getRandomNumber(496)+92);
            spawnTimer_ = 300;
        }
    }
}