更改下题，根据字符参数fillCharacter所包含的任何一种字符组成正方形，如果side等于5，fillCharacter等于#

Question

import java.applet.Applet;import java.awt.Button;import java.awt.Graphics;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JOptionPane;public class Task6_18 extends Applet {    int size ;   public void init(){   Button bt = new Button("点击我弹出输入框");    bt.addActionListener(new ActionListener(){   public void actionPerformed(ActionEvent e) {    String s = JOptionPane.showInputDialog(null, "请输入:");    size = Integer.parseInt(s);    repaint();   }  });  this.add(bt); }  public void paint(Graphics g){  if(size>0){   squareOfAsterisks(g,size);  } }  public void squareOfAsterisks(Graphics g, int size){  String str="";  int x=50,y=100;  for(int j=0;j<size;j++)    str+="* ";  for(int i=0;i<size;i++){   g.drawString(str, x, y);   y+=10;  } }}