NullPointerError

import greenfoot.*;
public class Player extends Actor
{
    private GifImage gif1;
    private GifImage gif2;
    private GreenfootImage image1;
    private GreenfootImage image2;
    private GreenfootImage image3;
    private int RunSpeed = 3;
    private int FallSpeed = 0;
    private int FallAcceleration = 1;
    private int CanJump = 0;
    private int CanWalkR = 0;
    private int CanWalkL = 0;
    private int HitCounter = 0;
    public Player()
    {
        gif1 = new GifImage("Player Running GIF R.gif");
        gif2 = new GifImage("Player Running GIF L.gif");
        image1 = new GreenfootImage("Player Still.png");
        image2 = new GreenfootImage("Player Jump R.png");
        image3 = new GreenfootImage("Player Jump L.png");
        GreenfootImage image = getImage();
        image.scale(22,55);
    }
    public void act() 
    {
        SpikeDeath();
        KeyCheck();
        NeedGravity();
        JumpReset();
        HitRoof();
        MoveFromGround();
    }   
    public void KeyCheck()
    {
        if (Greenfoot.isKeyDown("space") && !AtRoof() && CanJump == 0)
        {
            Jump();
            CanJump = 1;
        }
        else if (Greenfoot.isKeyDown("D") && !OnGround() && !ObjectRB() && !ObjectRT())
        {
            setImage(image2);
            GreenfootImage image = getImage();
            image.scale(50,67);
            MoveRight();
        }
        else if (Greenfoot.isKeyDown("A") && !OnGround() && !ObjectLB() && !ObjectLT())
        {
            setImage(image3);
            GreenfootImage image = getImage();
            image.scale(50,67);
            MoveLeft();
        }
        else if (Greenfoot.isKeyDown("D") && OnGround() && !ObjectRB() && !ObjectRT())
        {
            setImage(gif1.getCurrentImage());
            GreenfootImage image = getImage();
            image.scale(50,67);
            MoveRight();
        }
        else if (Greenfoot.isKeyDown("A") && OnGround() && !ObjectLB() && !ObjectLT())
        {
            setImage(gif2.getCurrentImage());
            GreenfootImage image = getImage();
            image.scale(50,67);
            MoveLeft();
        }
        else
        {
            setImage(image1);
            GreenfootImage image = getImage();
            image.scale(22,55);
        }
    }
    public void JumpReset()
    {
        if (CanJump == 1 && OnGround())
        {
            CanJump++;
        }
        else if (CanJump == 2 && OnGround())
        {
            CanJump++;
        }
        else if (CanJump == 3 && OnGround())
        {
            CanJump++;
        }
        else if (CanJump == 4 && OnGround())
        {
            CanJump++;
        }
        else if (CanJump == 5 && OnGround())
        {
            CanJump++;
        }
        else if (CanJump == 6 && OnGround())
        {
            CanJump++;
        }
        else if (CanJump == 7 && OnGround())
        {
            CanJump++;
        }
        else if (CanJump == 8 && OnGround())
        {
            CanJump++;
        }
        else if (CanJump == 9 && OnGround())
        {
            CanJump = 0;
        }
    }
    public void MoveRight()
    {
        setLocation (getX() + RunSpeed, getY());
    }
    public void MoveLeft()
    {
        setLocation (getX() - RunSpeed, getY());
    }
    public boolean OnGround()
    {
        Actor under = getOneObjectAtOffset (0, getImage().getHeight()/2, Obstacles.class);
        return under != null;
    }
    public boolean AtRoof()
    {
        Actor above = getOneObjectAtOffset (0, -(getImage().getHeight()/2), Obstacles.class);
        return above != null;
    }
    public boolean ObjectRB()
    {
        Actor rightB = getOneObjectAtOffset (getImage().getWidth()/2, getImage().getWidth()/3, Obstacles.class);
        return rightB != null;
    }
    public boolean ObjectRT()
    {
        Actor rightT = getOneObjectAtOffset (getImage().getWidth()/2, -(getImage().getWidth()/3), Obstacles.class);
        return rightT != null;
    }
    public boolean ObjectLB()
    {
        Actor leftB = getOneObjectAtOffset (-(getImage().getWidth()/2), getImage().getWidth()/3, Obstacles.class);
        return leftB != null;
    }
    public boolean ObjectLT()
    {
        Actor leftT = getOneObjectAtOffset (-(getImage().getWidth()/2), -(getImage().getWidth()/3), Obstacles.class);
        return leftT != null;
    }
    public boolean InGround()
    {
        Actor inground = getOneObjectAtOffset (0, (getImage().getHeight()/2)-5, Obstacles.class);
        return inground != null;
    }
    public boolean OnSpike()
    {
        Actor onspike = getOneObjectAtOffset (0, (getImage().getHeight()/2), Spikes.class);
        return onspike != null;
    }
    public void MoveFromGround()
    {
        if(InGround())
        {
            setLocation (getX(), getY() - 5);
        }
    }
    public void HitRoof()
    {
        if(AtRoof())
        {
            FallSpeed = 0;
            Gravity();
        }
    }
    public void NeedGravity()
    {
        if(OnGround())
        {
            FallSpeed = 0;
        }    
        else
        {
            Gravity();
        }
    }
    public void Gravity()
    {
        setLocation (getX(), getY() + FallSpeed);
        FallSpeed = FallSpeed + FallAcceleration;
        if (FallSpeed == 5)
        {
            FallSpeed = 5;
        }
    }
    public void Jump()
    {
        FallSpeed = -12;
        Gravity();
    }
    public void SpikeDeath()
    {
        if (OnSpike())
        {   
            HitCounter = HitCounter + 1;
            setLocation (74, 401);
            LoseHealth();
        }
        else if (HitCounter == 3)
        {
            Greenfoot.setWorld(new YouLose());
        }
    }
    public void LoseHealth()
    {
        Level1 Level1World = (Level1) getWorld();
        Health health = Level1World.getHealth();
        health.TakeDamage(1);
    }
}

import greenfoot.*;
public class Health extends Actor
{
    private GreenfootImage image1;
    private GreenfootImage image2;
    private GreenfootImage image3;
    private GreenfootImage image4;
    private int TotalHealth;
    public Health()
    {
        image1 = new GreenfootImage("3 Heart.png");
        image2 = new GreenfootImage("2 Heart.png");
        image3 = new GreenfootImage("1 Heart.png");
        image4 = new GreenfootImage("0 Heart.png");
        TotalHealth = 0;
    }
    public void act() 
    {
        if (TotalHealth == 0)
        {
            setImage (image1);
        }
        GreenfootImage image = getImage();
        image.scale(100,36);
    }   
    public void TakeDamage(int amount)
    {
        TotalHealth += amount;
        if (TotalHealth == 1)
        {
            setImage (image2);
        }
        else if (TotalHealth == 2)
        {
            setImage (image3);
        }
        else if (TotalHealth == 3)
        {
            setImage (image4);
        }
    }
}

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

/**
 * Write a description of class Level1 here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Level1 extends World
{
    private Health CurrHealth;
    /**
     * Constructor for objects of class Level1.
     * 
     */
    public Level1()
    {    
        super(1100, 450, 1); 
        prepare();
    }

    /**
     * Prepare the world for the start of the program.
     * That is: create the initial objects and add them to the world.
     */
    private void prepare()
    {
        BorderHorizontal borderHorizontal = new BorderHorizontal();
        addObject(borderHorizontal,550,10);
        BorderHorizontal borderHorizontal2 = new BorderHorizontal();
        addObject(borderHorizontal2,550,440);
        BorderVertical borderVertical = new BorderVertical();
        addObject(borderVertical,1090,225);
        BorderVertical borderVertical2 = new BorderVertical();
        addObject(borderVertical2,10,225);
        Vertical50 vertical50 = new Vertical50();
        addObject(vertical50,146,423);
        Vertical100 vertical100 = new Vertical100();
        addObject(vertical100,263,380);
        Vertical100 vertical1002 = new Vertical100();
        addObject(vertical1002,205,408);
        Horizontal100 horizontal100 = new Horizontal100();
        addObject(horizontal100,379,299);
        Horizontal200 horizontal200 = new Horizontal200();
        addObject(horizontal200,568,240);
        Vertical100 vertical1003 = new Vertical100();
        addObject(vertical1003,741,69);
        Vertical50 vertical502 = new Vertical50();
        addObject(vertical502,739,269);
        Vertical50 vertical503 = new Vertical50();
        addObject(vertical503,741,409);
        Horizontal50 horizontal50 = new Horizontal50();
        addObject(horizontal50,763,264);
        Horizontal100 horizontal1002 = new Horizontal100();
        addObject(horizontal1002,880,200);
        Vertical250 vertical250 = new Vertical250();
        addObject(vertical250,940,230);
        Horizontal50 horizontal502 = new Horizontal50();
        addObject(horizontal502,1072,367);
        Horizontal50 horizontal503 = new Horizontal50();
        addObject(horizontal503,968,294);
        Horizontal50 horizontal504 = new Horizontal50();
        addObject(horizontal504,1065,231);
        Horizontal50 horizontal505 = new Horizontal50();
        addObject(horizontal505,967,163);
        Player player = new Player();
        addObject(player,74,401);
        Spike1 spike1 = new Spike1();
        addObject(spike1,177,412);
        Spike1 spike12 = new Spike1();
        addObject(spike12,235,412);
        Spike1 spike13 = new Spike1();
        addObject(spike13,449,412);
        Spike1 spike14 = new Spike1();
        addObject(spike14,539,412);
        Health CurrHealth = new Health();
        addObject(CurrHealth,76,41);
    }
    public Health getHealth()
    {
        return CurrHealth;
    }
}