Graphic2D画了一个矩形, 如何使用斜线填充？

Question

一部分源码，你看一下。不懂再说   
         g.setPaint(coveColor);
             Composite oldComposite2=g.getComposite();
             g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER,ROP2));
             Shape oudClipShape2=g.getClip();
             g.setClip(clipShape);
             for (int i=0;i<width;i=i+10){
               double x1=i;
               double y1=0;
               double x2=1000;
               double y2=1000-i;
               java.awt.geom.Point2D p=new java.awt.geom.Point2D.Double(x1,y1);
               java.awt.geom.Point2D q=new java.awt.geom.Point2D.Double(x2,y2);
               g.draw(new Line2D.Double(p,q));
             }
             for (int i=0;i<height;i=i+10){
               double x1=0;
               double y1=i;
               double x2=1000-i;
               double y2=1000;
               Point2D p=new Point2D.Double(x1,y1);
               Point2D q=new Point2D.Double(x2,y2);
               g.draw(new Line2D.Double(p,q));
             }
             g.setClip(oudClipShape2);
             g.setComposite(oldComposite2);

Answer 1

哦，还是需要自己一条条地画啊！
请问这两句是干什么的？
 g.setClip(oudClipShape2);
 g.setComposite(oldComposite2);望指教？

Answer 2

Rectangle r =getBounds();
      int hlines = r.height / 10;
      int vlines = r.width / 10;      g2D.setColor(Color.darkGray);
      for (int i = 1; i <= hlines; i++) {
         g2D.drawLine(0, i * 10, r.width, i * 10);
      }
      for (int i = 1; i <= vlines; i++) {
          g2D.drawLine(i * 10, 0, i * 10, r.height);
        }

Answer 3

请问这两句是干什么的？
 g.setClip(oudClipShape2);
 g.setComposite(oldComposite2);