这是什么意思? public void mouseReleased(MouseEvent e) {}运行时,这句出错,

求求你下回抄程序也吵得认真点吧，错误太多了，这个是改完的，自己看吧

package com.opt.test;

import java.awt.*;
import java.awt.event.*;
class MyCanvas extends Canvas implements MouseListener
{
int left=-1,right=-1;
int x=-1,y=-1;
MyCanvas()
{
setSize(200,200);
setBackground(Color.pink);
super.addMouseListener(this);
}
public void paint(Graphics g)
{
if(left==-1)
{
g.drawString("按下了鼠标左键",x,y);
}
else if(right==-1)
{
g.drawString("按下了鼠标右键",x,y);
}
}
public void mousePressed(MouseEvent e)
{
x=e.getX();
y=e.getY();
if(e.getModifiers()==InputEvent.BUTTON1_MASK)
{
left=1;
right=-1;
repaint();
}
else if(e.getModifiers()==InputEvent.BUTTON2_MASK)
{
right=1;
left=-1;
repaint();
}
}
public void mouseReleased(MouseEvent e)