package corsoDrZito.lez3.es4;

import java.applet.Applet;
import java.awt.*;

public class esercizio4 extends Applet implements Runnable
{
	public void init()
	{
		int num = 4;

		d = getSize();

		String param = getParameter("num");
		if (param!=null) num = Integer.parseInt(param);

		palle = new Palla[num];
		for(int i=0;i<palle.length;i++)
			palle[i] = new Palla(d);

		im = createImage(d.width, d.height);
		myg = im.getGraphics();

		setBackground(new Color(48,64,96));

		t = new Thread(this);
		t.start();
	}

	public synchronized void update(Graphics g) { paint(g); }
	public synchronized void paint(Graphics g)
	{
		myg.clearRect(0, 0, d.width, d.height);

		for(int i=0;i<palle.length;i++)
			palle[i].paint(myg);

		g.drawImage(im, 0, 0, this);
	}

	public void run()
	{
		Thread.currentThread().setPriority(Thread.NORM_PRIORITY);
		do
		{
			for(int i=0;i<palle.length;i++)
				palle[i].muovi();
			repaint();
			try
			{
				Thread.currentThread();
				Thread.sleep(10L);
			}
			catch(InterruptedException ex) {}
		}
		while(true);
	}

	private Palla[] palle;

	private Image im;
	private Graphics myg;
	private Dimension d;
	private Thread t;
}

package corsoDrZito.lez3.es4;

import java.awt.Graphics;
import java.awt.Dimension;
import java.awt.Color;

public class Palla
{
	public Palla(Dimension d)
	{
		super();

		radius = (float)Math.random()*Math.min(d.width, d.height) / 10.f + 6f;
		r = (int)radius;

		pos_x = (float)(Math.random()*(d.width  - r));

		pos_y = (float)(Math.random()*(d.height - r));

		vel_x = (float)Math.random()*75.f + 25.f;
		vel_y = (float)Math.random()*75.f + 25.f;

		x = (int)pos_x;
		y = (int)pos_y;

		bounds = d;

		color = new Color( (int)(128+64*Math.random()), (int)(128+64*Math.random()), (int)(128+64*Math.random()) );

		marker = new int[markmax][2];

		millis = System.currentTimeMillis();
	}

	public void muovi()
	{
		long currentMillis = System.currentTimeMillis();
		long delta = currentMillis - millis;
		markcounter += delta;

		pos_x += vel_x * (delta / 1000.f);

		vel_y += acc_y * (delta / 1000.f);
		pos_y += vel_y * (delta / 1000.f);


		x = (int)pos_x;
		y = (int)pos_y;

		if (markcounter > markdelay)
		{
			marker[markindex][0] = x + r / 2;
			marker[markindex][1] = y + r / 2;
			markindex = ++markindex % markmax;
			markcounter = delta % markdelay;
		}

		if(x + r >= bounds.width ) vel_x = - Math.abs(vel_x);
		if(x < 0) vel_x = Math.abs(vel_x);
		if(y + r >= bounds.height) vel_y = - Math.abs(vel_y);
		if(y < 0) vel_y = Math.abs(vel_y);

		millis = currentMillis;

		try
		{
			Thread.currentThread();
			Thread.sleep(5L);
		}
		catch(InterruptedException ex) {}
	}

	public synchronized void paint(Graphics g)
	{
		g.setColor(Color.black);
		g.fillOval( x, y, r, r );
/*
		int px = (x+r+100 < bounds.width)?x+r: x-100;
		g.drawString( "vx:"+vel_x, px, y );
		g.drawString( "vy:"+vel_y, px, y + 12 );

		g.setColor(color);
		g.drawLine(x+r/2, y+r/2, x+r/2+(int)vel_x, y+r/2+(int)vel_y);
*/
		g.setColor(color);
		for(int i=0;i<marker.length; i++)
			g.fillRect( marker[i][0], marker[i][1], 2, 2);
	}

	private static long millis;
	private int r;
	private int x;
	private int y;
	private float radius;
	private float pos_x;
	private float vel_x;
	private float acc_x = 0.0f;
	private float pos_y;
	private float vel_y;
	private float acc_y = 9.81f;
	private Dimension bounds;
	private Color color;
	private int[][] marker;
	private int markindex;
	private int markmax = 20;
	private long markcounter;
	private long markdelay = 500; // millis
}