[Abdelhamidem]

Thank you so much for your help, and all that work you've done. I've just found a solution, using a javax.Swing timer:

I changed the graphique1 class to this (by the way, i renamed it Graphique)

Code:

package montecarlo;

import javax.swing.*;
import javax.swing.event.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;

public class Graphique extends JPanel implements ActionListener {

    int X[] = new int[10000];
    int Y[] = new int[10000];
    int min, max;
    Random rand = new Random();
    int randX = 0;
    int randY = 0;
    boolean functionDrawed = false;
    double zoom = 1;
    Integrale integrale;
    javax.swing.Timer t;

    public Graphique(Integrale I) {
        integrale = I;
        min = (int) I.borneMin - 100;
        max = (int) I.borneMax + 100;
        for (int i = min; i < max; i++) {
            X[i - min] = (int) zoom * i + 300;
            Y[i - min] = (int) (225 - zoom * I.evaluer(i));
        }
        this.setPreferredSize(new java.awt.Dimension(600, 450));
        repaint();
        t = new javax.swing.Timer(100, this);
        t.start();
    }

    @Override
    public void paintComponent(java.awt.Graphics g) {
        if (!functionDrawed) {
            g.setColor(new java.awt.Color(255, 255, 255));
            g.fill3DRect(0, 0, 599, 449, true);
            g.setColor(new java.awt.Color(0, 0, 0));
            g.drawPolygon(X, Y, max - min);
            functionDrawed = true;
        }
        randX = rand.nextInt(100) + -5 + 300;
        randY = 225 - rand.nextInt(100);
        if ((225 - zoom * integrale.evaluer((randX - 300) / zoom)) > randY) {
            g.setColor(new java.awt.Color(255, 0, 0));
        } else {
            g.setColor(new java.awt.Color(0, 0, 255));
        }
        g.drawLine(randX, randY, randX, randY);
    }

    public void actionPerformed(ActionEvent e) {
        repaint();
    }
   
}

and it works perfectly!