没有使用Cos和Sin或高级三角方程的方形旋转

Question

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

class Point {

    private int x;
    private int y;

    public Point(){
      x=0;
      y=0;
    }

    public Point(int xx,int yy){
        x=xx;
        y=yy;
    }

    public void setPint(int xx,int yy){
        x=xx;
        y=yy;
    }

    public int getX(){
        return x;
    }

    public int getY(){
        return y;
    }
}
public void paintComponent(Graphics g) {

    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D)g;
    g2.setColor(Color.blue);

    double u=0.1;

    int Sqr=10;

    //Point P,Q,S,R;
    Point[][] points=new Point[4][4];

    points[0][0]=new Point(100,100);
    points[0][1]= new Point(300,100);
    points[0][2]= new Point(100,300);
    points[0][3]= new Point(300,300);

    g2.drawLine(points[0][0].getX(), points[0][0].getY(), points[0][1].getX(), points[0][1].getY());
    g2.drawLine(points[0][3].getX(), points[0][3].getY(), points[0][1].getX(), points[0][1].getY());
    g2.drawLine(points[0][2].getX(), points[0][2].getY(), points[0][3].getX(), points[0][3].getY());
    g2.drawLine(points[0][0].getX(), points[0][0].getY(), points[0][2].getX(), points[0][2].getY());

    //points[0][0]=P;
    //points[0][1]=Q;
    //points[0][2]=S;
    //points[0][3]=R;

    for(int i=0;i<4;i++){
        for(int j=0;j<4;j++){
            //points[i][j]=new Point();
            points[i+1][j].setPint((int)((1-u)* points[i][j].getX()+ u * points[i][j+1].getX()),(int) ((1-u) * points[i][j].getY()+ u * points[i][j+1].getY()));
        }
//        for(int line=0;line<4;line++){
//            g2.drawLine(points[i][line].getX(),points[i][line].getY(),points[i][line+1].getX(),points[i][line+1].getY());
//        }
    }

//    System.out.println("#####");
//    System.out.println(points[0][0].getX());
//    System.out.println(points[0][0].getY());
//    System.out.println("#####");



//
//P1.setPint((int) ((1-u)*P.getX()+ u* Q.getX()), (int) ((1-u)*P.getY()+ u* Q.getY()));
//Q1.setPint((int) ((1-u)*Q.getX()+ u* R.getX()), (int) ((1-u)*Q.getY()+ u* R.getY()));
//R1.setPint((int) ((1-u)*R.getX()+ u* S.getX()), (int) ((1-u)*R.getY()+ u* S.getY()));
//S1.setPint((int) ((1-u)*S.getX()+ u* P.getX()), (int) ((1-u)*S.getY()+ u* P.getY()));
//
//g2.drawLine(points[0][0].getX(), points[0][0].getY(), points[0][1].getX(), points[0][1].getY());
//g2.drawLine(points[0][1].getX(), points[0][1].getY(), points[0][3].getX(), points[0][3].getY()); 
//g2.drawLine(points[0][3].getX(), points[0][3].getY(), points[0][2].getX(), points[0][2].getY());
//g2.drawLine(points[0][2].getX(), points[0][2].getY(), points[0][0].getX(), points[0][0].getY());



  }

  

线程中的异常＆＃34; AWT-EventQueue-0＆＃34;显示java.lang.NullPointerException

     

在Hello2DPanel.paintComponent（Hello2D.java:78）处   javax.swing.JComponent.paint（JComponent.java:1056）at   javax.swing.JComponent.paintChildren（JComponent.java:889）at   javax.swing.JComponent.paint（JComponent.java:1065）at   javax.swing.JComponent.paintChildren（JComponent.java:889）at   javax.swing.JComponent.paint（JComponent.java:1065）at   javax.swing.JLayeredPane.paint（JLayeredPane.java:586）at at   javax.swing.JComponent.paintChildren（JComponent.java:889）at   javax.swing.JComponent.paintToOffscreen（JComponent.java:5217）at   javax.swing.RepaintManager中的$ PaintManager.paintDoubleBuffered（RepaintManager.java:1579）     在   javax.swing.RepaintManager中的$ PaintManager.paint（RepaintManager.java:1502）     在javax.swing.RepaintManager.paint（RepaintManager.java:1272）at   javax.swing.JComponent.paint（JComponent.java:1042）at   java.awt.GraphicsCallback $ PaintCallback.run（GraphicsCallback.java:39）     在   sun.awt.SunGraphicsCallback.runOneComponent（SunGraphicsCallback.java:79）     在   sun.awt.SunGraphicsCallback.runComponents（SunGraphicsCallback.java:116）     在java.awt.Container.paint（Container.java:1975）at   javax.swing.RepaintManager $ 4.run（RepaintManager.java:842）at   javax.swing.RepaintManager $ 4.run（RepaintManager.java:814）at   java.security.AccessController.doPrivileged（Native Method）at   java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:76）     在   javax.swing.RepaintManager.paintDirtyRegions（RepaintManager.java:814）     在   javax.swing.RepaintManager.paintDirtyRegions（RepaintManager.java:789）     在   javax.swing.RepaintManager.prePaintDirtyRegions（RepaintManager.java:738）     在javax.swing.RepaintManager.access $ 1200（RepaintManager.java:64）at   javax.swing.RepaintManager中的$ ProcessingRunnable.run（RepaintManager.java:1732）     at java.awt.event.InvocationEvent.dispatch（InvocationEvent.java:311）     在java.awt.EventQueue.dispatchEventImpl（EventQueue.java:756）at   java.awt.EventQueue.access $ 500（EventQueue.java:97）at   java.awt.EventQueue $ 3.run（EventQueue.java:709）at   java.awt.EventQueue $ 3.run（EventQueue.java:703）at   java.security.AccessController.doPrivileged（Native Method）at   java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:76）     在java.awt.EventQueue.dispatchEvent（EventQueue.java:726）at   java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:201）     在   java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java:116）     在   java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:105）     在   java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:101）     在   java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:93）     at java.awt.EventDispatchThread.run（EventDispatchThread.java:82）   线程中的异常＆＃34; AWT-EventQueue-0＆＃34;显示java.lang.NullPointerException     在Hello2DPanel.paintComponent（Hello2D.java:78）at   javax.swing.JComponent.paint（JComponent.java:1056）at   javax.swing.JComponent.paintChildren（JComponent.java:889）at   javax.swing.JComponent.paint（JComponent.java:1065）at   javax.swing.JComponent.paintChildren（JComponent.java:889）at   javax.swing.JComponent.paint（JComponent.java:1065）at   javax.swing.JLayeredPane.paint（JLayeredPane.java:586）at at   javax.swing.JComponent.paintChildren（JComponent.java:889）at   javax.swing.JComponent.paintToOffscreen（JComponent.java:5217）at   javax.swing.RepaintManager中的$ PaintManager.paintDoubleBuffered（RepaintManager.java:1579）     在   javax.swing.RepaintManager中的$ PaintManager.paint（RepaintManager.java:1502）     在javax.swing.RepaintManager.paint（RepaintManager.java:1272）at   javax.swing.JComponent.paint（JComponent.java:1042）at   java.awt.GraphicsCallback $ PaintCallback.run（GraphicsCallback.java:39）     在   sun.awt.SunGraphicsCallback.runOneComponent（SunGraphicsCallback.java:79）     在   sun.awt.SunGraphicsCallback.runComponents（SunGraphicsCallback.java:116）     在java.awt.Container.paint（Container.java:1975）at   javax.swing.RepaintManager $ 4.run（RepaintManager.java:842）at   javax.swing.RepaintManager $ 4.run（RepaintManager.java:814）at   java.security.AccessController.doPrivileged（Native Method）at   java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:76）     在   javax.swing.RepaintManager.paintDirtyRegions（RepaintManager.java:814）     在   javax.swing.RepaintManager.paintDirtyRegions（RepaintManager.java:789）     在   javax.swing.RepaintManager.prePaintDirtyRegions（RepaintManager.java:738）     在javax.swing.RepaintManager.access $ 1200（RepaintManager.java:64）at   javax.swing.RepaintManager中的$ ProcessingRunnable.run（RepaintManager.java:1732）     at java.awt.event.InvocationEvent.dispatch（InvocationEvent.java:311）     在java.awt.EventQueue.dispatchEventImpl（EventQueue.java:756）at   java.awt.EventQueue.access $ 500（EventQueue.java:97）at   java.awt.EventQueue $ 3.run（EventQueue.java:709）at   java.awt.EventQueue $ 3.run（EventQueue.java:703）at   java.security.AccessController.doPrivileged（Native Method）at   java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:76）     在java.awt.EventQueue.dispatchEvent（EventQueue.java:726）at   java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:201）     在   java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java:116）     在   java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:105）     在   java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:101）     在   java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:93）     在java.awt.EventDispatchThread.run（EventDispatchThread.java:82）

绘制一个正方形，然后通过参数u在第一个缩小的尺寸内绘制第二个正方形，依此类推 P1x =（（1-u）* Px）+（u * Qx）
P1y =（（1 - u）* Py）+（u * Qy） 类似地，Q，R，S 注意：不使用Cos和Sin或高级三角方程。 哪里错了？