为什么背景色设置后没有改变

Question

import java.awt.*;
import java.util.*;public class Clock extends javax.swing.JApplet{
 private Color butterscotch=new Color(255,204,102);
 private String lastTime="";
 
 public void init(){
  setBackground(Color.black);
  }
 
 public void paint(Graphics screen){
   Graphics2D screen2D=(Graphics2D)screen;
   Font type=new Font("Monospaced",Font.BOLD,20);
   screen2D.setFont(type);
   GregorianCalendar day=new GregorianCalendar();
   String nowTime=day.getTime().toString();
   screen2D.setColor(Color.black);
   screen2D.drawString(lastTime,5,25);
   screen2D.setColor(butterscotch);
   screen2D.drawString(nowTime,5,25);
   try{
      Thread.sleep(1000);
    }
   catch(InterruptedException e){
   
    }
   lastTime=nowTime;
   repaint();
  }
}

Answer 1

不知道是不是这个意思
import java.awt.*;
import java.util.*;public class Clock extends javax.swing.JApplet{
private Color butterscotch=new Color(111,111,111);
private String lastTime=""; public void init(){
setBackground(Color.BLACK);
}

public void changeColor(Color color){
setBackground(color);
} public void paint(Graphics screen){
Graphics2D screen2D=(Graphics2D)screen;
Font type=new Font("Monospaced",Font.BOLD,10);
screen2D.setFont(type);
GregorianCalendar day=new GregorianCalendar();
String nowTime=day.getTime().toString();
screen2D.drawString(lastTime,5,25);
screen2D.setColor(butterscotch);
screen2D.drawString(nowTime,5,25);
try{
Thread.sleep(1000);
}
catch(InterruptedException e){ }
this.changeColor(Color.blue);
this.setVisible(false);
this.setVisible(true);
lastTime=nowTime;
repaint();
}
}

Answer 2

还是这样?
import java.awt.*;
import java.util.*;public class Clock extends javax.swing.JApplet{
private Color butterscotch=new Color(0,255,0);
private String lastTime=""; public void init(){
setBackground(Color.BLACK);
}

public void changeColor(Color color){
setBackground(color);
} public void paint(Graphics screen){
Graphics2D screen2D=(Graphics2D)screen;
Font type=new Font("Monospaced",Font.BOLD,20);
screen2D.setFont(type);
GregorianCalendar day=new GregorianCalendar();
String nowTime=day.getTime().toString();
screen2D.clearRect(0, 0, 10000, 10000);
screen2D.setColor(butterscotch);
screen2D.drawString(lastTime,5,25);

screen2D.setColor(Color.WHITE);
screen2D.drawString(nowTime,5,50);
try{
Thread.sleep(1000);
}
catch(InterruptedException e){ }
/*//this.changeColor(Color.blue);
System.out.println(screen2D.getBackground());
this.setVisible(false);
this.setVisible(true);*/
lastTime=nowTime;
repaint();
}
}

Answer 3

问题解决了 
谢谢楼上的wuhaozhiyuan(飘)