CODE

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

public class MyWorld extends World{

public MyWorld(){

super(1200, 800, 1);

Player player = new Player();

Friend friend = new Friend();

this.addObject(player, 1050, 225);

this.addObject(friend, 900, 600);

}

}

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

import javax.swing.JOptionPane;

public class Balloon extends Actor{

boolean enteredValues = false;

public void act(){

if(!enteredValues){

String str1 = JOptionPane.showInputDialog("Enter Balloon's vertical speed (m/s)");

horizontalSpeed = Integer.parseInt(str1);

String str2 = JOptionPane.showInputDialog("Enter acceleration (m/s^2)");

acceleration = Integer.parseInt(str2);

enteredValues = true;

}

fall();

if(getOneIntersectingObject(Friend.class) != null)

this.getWorld().removeObject(this);

else if(this.getY()+1 == getWorld().getHeight())

this.getWorld().removeObject(this);

}

int horizontalSpeed;

int verticalSpeed;

int acceleration;

boolean timeTaken = false;

long time1;

int initialX;

int initialY;

public void fall(){

if(!timeTaken){

time1 = System.currentTimeMillis();

timeTaken = true;

initialX = getX();

initialY = getY();

}

int newX = (int)(horizontalSpeed*(((float)(System.currentTimeMillis()-time1))/1000));

int newY = (int)(acceleration/2*Math.pow((((float)(System.currentTimeMillis()-time1))/1000), 2));

setLocation(initialX - newX, initialY + newY);

}

}

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

import javax.swing.JOptionPane;

public class Friend extends Actor{

boolean isRunning = false;

int runningSpeed;

public void act() {

if(!isRunning){

isRunning = true;

String str = JOptionPane.showInputDialog("Enter UFO's speed (m/s)");

runningSpeed = Integer.parseInt(str);

}

run();

}

boolean touchedBoarder = false;

boolean timeTaken = false;

long time1;

public void run(){

if(getX()>895)

touchedBoarder = false;

if(getX()<5)

touchedBoarder = true;

if(!timeTaken){

time1 = System.currentTimeMillis();

timeTaken = true;

}

if(touchedBoarder){

if(System.currentTimeMillis() - time1>40){

setLocation(getX()+runningSpeed/20, getY());

timeTaken = false;

}

}

else if(!touchedBoarder){

if(System.currentTimeMillis() - time1>40){

setLocation(getX()-runningSpeed/20, getY());

timeTaken = false;

}

}

}

}

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

public class Player extends Actor{

public void act(){

throwBalloon();

}

boolean isThrowing = false;

boolean finalThrow = true;

public void throwBalloon(){

if(Greenfoot.isKeyDown("space")){

this.setImage("alien1.png");

Greenfoot.delay(10);

this.setImage("alien2.png");

isThrowing = true;

}

if(isThrowing && finalThrow){

isThrowing = false;

finalThrow = false;

Balloon balloon = new Balloon();

World world = getWorld();

world.addObject(balloon, this.getX(), this.getY());

Greenfoot.delay(5);

}

}

}