Calcul d'heure

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
class Heure extends JFrame
{
private int heure,vraiHeure,min,seconde;
private int[] x2={200,209,217,225,233,240,248,254,260,265,270,
274,277,278,279,280,279,278,277,274,270,
265,260,254,248,240,233,225,217,209,200,
192,184,176,168,160,153,147,141,136,130,
127,124,122,121,120,121,122,124,127,130,
136,141,147,153,160,168,176,184,192};
private int[] y2={70,71,72,74,77,80,86,91,97,103,110,
118,126,134,142,150,159,167,175,183,190,
197,204,209,214,220,224,227,228,229,230,
229,228,227,224,220,214,209,204,197,190,
183,175,167,159,150,142,134,126,118,110,
103,97,91,86,80,77,74,72,71};
private int[] Tx2={195,240,270,280,270,240,195,155,125,115,120,150};
private int[] Ty2={70,80,110,155,195,225,240,225,195,155,115,80};
private int[] Hx2={200,207,213,220,225,230,236,240,244,247,248,249,
250,249,248,247,244,236,230,225,213,220,213,207,200,
194,188,181,175,170,165,161,157,154,152,151,150,151,
152,154,157,161,165,170,175,181,188,194};
private int[] Hy2={100,101,102,104,107,111,115,120,125,131,138,144,150,
157,163,170,175,181,186,190,194,197,198,199,200,
199,198,197,194,190,186,181,175,170,163,157,150,144,
138,131,125,120,115,111,107,104,102,101};
private final int x1=200,y1=150;
private boolean quar=true,demi=true,moinquar=true;

public Heure()
{
super("Heure");
setBounds(300,200,400,300);
Container con = getContentPane();
con.setLayout(null);
Date date = new Date();
System.out.println(Hx2.length);
System.out.println(Hy2.length);
setDefaultCloseOperation(this.EXIT_ON_CLOSE);
heure = date.getHours();
vraiHeure = heure;
if(heure > 12)
heure=(heure-=12)*4;
min = date.getMinutes();
seconde = date.getSeconds();
if(min >= 15 && min < 30)
{
heure++;
quar = false;
}
if(min >= 30 && min < 45)
{
heure+=2;
quar = false;
demi = false;
}
if(min >= 45)
{
heure+=3;
quar = false;
demi = false;
moinquar = false;
}
System.out.println(vraiHeure+":"+min+" "+seconde);
setVisible(true);
setResizable(false);
second();
}

public void paint(Graphics g)
{
g.clearRect(0,0,400,300);
g.setColor(Color.orange);
g.fillRect(100,50,200,200);
g.setColor(Color.white);
g.fillOval(100,50,200,200);
g.setColor(Color.green);
g.drawLine(x1,y1,x2[min],y2[min]);
g.drawLine(x1,y1,Hx2[heure],Hy2[heure]);
g.setColor(Color.red);
g.drawLine(x1,y1,x2[seconde],y2[seconde]);
g.setColor(Color.blue);
g.drawString("12",Tx2[0],Ty2[0]);
for(int i=1;i < 12;i++)
{
g.drawString(String.valueOf(i),Tx2[i],Ty2[i]);
}
g.setColor(Color.black);
if(seconde<10&&min<10)
g.drawString(vraiHeure+":0"+min+" 0"+seconde,180,270);
if(seconde>=10&&min<10)
g.drawString(vraiHeure+":0"+min+" "+seconde,180,270);
if(seconde<10&&min>=10)
g.drawString(vraiHeure+":"+min+" 0"+seconde,180,270);
if(seconde>=10&&min>=10)
g.drawString(vraiHeure+":"+min+" "+seconde,180,270);
}

private void second()
{
Thread sec = new Thread();
while(true)
{
try
{
sec.sleep(1000);
}catch(Exception err)
{
}
if(seconde==59)
{
seconde = 0;
if(min==59)
{
min = 0;
if(heure==48)
{
heure = 0;
vraiHeure = 0;
}
else
{
heure++;
vraiHeure++;
}
quar=true;
demi=true;
moinquar=true;
}
else
min++;
}
else
seconde++;
if(min >= 15 && min < 30 && quar)
{
heure++;
quar = false;
}
if(min >= 30 && min < 45 && demi)
{
heure++;
demi = false;
}
if(min >= 45 && moinquar)
{
heure++;
moinquar = false;
}
repaint();
}
}

public static void main(String[] args)
{
new Heure();
}
}

 function msToTime(duration) {
  var milliseconds = parseInt((duration % 1000) / 100),
    seconds = Math.floor((duration / 1000) % 60),
    minutes = Math.floor((duration / (1000 * 60)) % 60),
    hours = Math.floor((duration / (1000 * 60 * 60)) % 24);

  hours = (hours < 10) ? "0" + hours : hours;
  minutes = (minutes < 10) ? "0" + minutes : minutes;
  seconds = (seconds < 10) ? "0" + seconds : seconds;

  return hours + ":" + minutes + ":" + seconds + "." + milliseconds;
}

  var d1 = new Date();
  d1.setHours(6, 0, 0); // heure1="6:00";
  
   var d2 = new Date();
  d2.setHours(18, 0, 0); // heure2="18:00";
  
  var diff = Math.abs(d2 - d1); // retourne la différence en millisecondes
  console.log(msToTime(diff)); // affiche dans la console la durée en Heures:Minutes:Secondes
  
  var tiers=diff/3;
  console.log(msToTime(tiers)); // affiche dans la console la durée en Heures:Minutes:Secondes
  
  var tiers1 = new Date(d1.getTime() + tiers);
  console.log(tiers1);
  
  var tiers2 =  new Date(tiers1.getTime() + tiers);
  console.log(tiers2);
  
  var tiers3 =  new Date(tiers2.getTime() + tiers);
  console.log(tiers3);
  

  var d2 = new Date();
  d2.setDate(d2.getDate() + 1);
  d2.setHours(6, 0, 0); // heure2="6:00"  le lendemain;
  
   var d1 = new Date();
  d1.setHours(18, 0, 0); // heure1="18:00";