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

class?DrawLinePanel1?extends?JPanel
{

?private?static?final?long?serialVersionUID?=?1L;
?private?int?startX?=?0;
?private?int?startY?=?0;
?private?int?endX?=?0;
?private?int?endY?=?0;

?public?DrawLinePanel1（）?
?{

??addMouseListener（new?MouseHandler（））;
}

?private?class?MouseHandler?extends?MouseAdapter?
?{
??public?void?mousePressed（MouseEvent?event）?{//?鼠標按下時
???if?（event.getButton（）?==?MouseEvent.BUTTON1）?
???{
????startX?=?event.getX（）;
????startY?=?event.getY（）;
???}
??}

??public?void?mouseReleased（MouseEvent?event）?{//?鼠標釋放時
	???if?（event.getButton（）?==?MouseEvent.BUTTON1）?
	???{
	?????endX=event.getX（）;
	?????endY=event.getY（）;
	?????Container?c?=?（Container）?event.getSource（）;
	?????Graphics?g?=?c.getGraphics（）;?//get?a?graphics?context
	?????g.setColor（Color.BLUE）;

	????
	?????DDA（startXstartYendXendYg）;//下面注釋的是中點畫線算法和Bresenham算法
	?????
//	?????MidPoint（startXstartYendXendYg）;
//	?????Bresenham（startXstartYendXendYg）;
	???}
	???
	???
	???}?
??private?void?DDA（int?x0?int?y0?int?x1?int?y1Graphics?g）?
??{
	?????double?dxdyk;
	?????dx?=?x1-x0;dy?=?y1-y0;
	?????k?=?dy/dx;
	?????
?	?if（Math.abs（k）?>=?1.0）
?	?{
?		?
?		?int?y?=?0;
?		?k?=??dx/dy;
	????	?double?x?=?Math.max（x1?x0）;
	????	?if（k?>=?0）
	????		?x?=?Math.min（x1?x0）;
	????	?
	????	?for（y?=?Math.min（y1y0）;?y?<=?Math.max（y0?y1）;?y++）
		?????{
	????		?g.drawLine（（int）（x+0.5）?y?（int）（x+0.5）y）;
		?????????x?=?x+k;
		?????}
	????}
	????else
	????{
	????	?int?x?=?0;
	????	?double?y?=?Math.min（y0y1）;
	????	?if（k>-1?&&?k<0）
	????		?y?=?Math.max（y0y1）;
		?????for（x?=?Math.min（x0x1）;?x?<=?Math.max（x0x1）;?x++）
		?????{
		????	?g.drawLine（x?（int）（y+0.5）?x?（int）（y+0.5））;
		?????????y?=?y+k;
		?????}
?	?}?
??}
??private?void?MidPoint（int?x0?int?y0?int?x1?int?y1Graphics?g）{
	??
	??int?abd1d2dx?=?0y;double?k?=?0;
	?????a=y0-y1;b=x1-x0;
	?????k?=?（-1.0*a）/b;
	?????
	?????if（Math.abs（k）<=1）
	?????{
	????	?if（k>=0）
	????	?{
		????	?a?=?Math.abs（y1-y0）*-1;??b?=?Math.abs（x1-x0）;
			?????d?=?2*a?+?b;
		????	?d1?=?2*a;?d2?=?2*（a+b）;
		????	?x?=?Math.min（x0x1）;?y?=?Math.min（y0y1）;
		????	?g.drawLine（x?y?x?y）;
		????	?while（x			????	?{
			????		?if（d<0）
			????		?	{x++;?y++;?d+=d2;}
			????		?else
			????		????{x++;d+=d1;}
			????		?g.drawLine（x?y?x?y）;
			????	?}
	????	?}
	????	?else
	????	?{
	????		?//a=Math.max（y1y0）-Math.min（y1?y0）;b=Math.max（x1x0）-Math.min（x1x0）;
	????		?a?=?Math.abs（y1-y0）;??b?=?Math.abs（x1-x0）;
	????		?d=2*a-b;d2=2*a-2*b;d1=2*a;???
	????		?x?=Math.min（x1?x0）;
	????		?y?=?Math.max（y1?y0）;
	????		?g.drawLine（x?y?x?y）;
	????	?????while?（x	????	?????{??
	????	????	?if?（d>0）????
	????	?????	?{
	????	????		?x++;
	????	????		?y--;
	????	????		?d+=d2;
	????	????	?}??
	????	?????????else????
	????	?????????{