qiugen.java

计算方法课

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.lang.*;
public class qiugen extends Applet implements ActionListener{
  Button A, B, C, D;
  boolean choosea, chooseb, choosec, choosed;
  double error=0.001;
  public void init() {
    A = new Button("f(x)=x-2sinx");
    B = new Button("二分法");
    C = new Button("牛顿法");
    D = new Button("弦截法");
    add(A);
    add(B);
    add(C);
    add(D);
    A.addActionListener(this);
    B.addActionListener(this);
    C.addActionListener(this);
    D.addActionListener(this);
  }

  public void actionPerformed(ActionEvent ae) {
    String str = ae.getActionCommand();
    if (str.equals("f(x)=x-2sinx")) {
      choosea = true; chooseb=false;choosec=false;choosed=false;
      repaint();
    }
    if (str.equals("二分法")) {
      chooseb = true; choosec=false;choosed=false;
      repaint();
    }
    if (str.equals("牛顿法")) {
      choosec = true; chooseb=false;choosed=false;
      repaint();
    }
    if (str.equals("弦截法")) {
      choosed = true; chooseb=false;choosec=false;
      repaint();
    }
  }
  public double f(double x){
    return x-2*Math.sin(x);
  }
  public double fdao(double x){
    return 1-2*Math.cos(x);
  }

  public void paint(Graphics g) { //绘图
    g.drawLine(50, 350, 700, 350);
    g.drawLine(50, 30, 50, 550);
    g.drawLine(50, 30, 54, 39);
    g.drawLine(50, 30, 46, 39);
    g.drawLine(700, 350, 695, 345);
    g.drawLine(700, 350, 695, 355);
    g.drawString("x", 705, 360);
    g.drawString("y", 40, 32);
    g.drawString("0", 40, 355);
    g.drawLine(50, 420, 55, 420);//y轴1:140
    g.drawString("-0.5", 20, 425);
    g.drawLine(50, 490, 55, 490);
    g.drawString("-1", 30, 495);
    g.drawLine(50, 280, 55, 280);
    g.drawString("0.5", 30, 285);
    g.drawLine(50, 210, 55, 210);
    g.drawString("1", 40, 215);
    g.drawLine(50, 140, 55, 140);
    g.drawString("1.5", 30, 145);
    g.drawLine(50, 70, 55, 70);
    g.drawString("2", 40, 75);
    g.drawLine(50 + 200, 350, 50 + 200, 345);
    g.drawString("1", 248, 365); //x轴比例为1：200
    g.drawLine(50 + 400, 350, 50 + 400, 345);
    g.drawString("2", 448, 365);
    g.drawLine(50 + 600, 350, 50 + 600, 345);g.drawString("3", 648, 365);
    g.drawLine(500, 40, 523, 40);
    g.drawString("原方程曲线", 525, 45);
    g.setColor(Color.blue);
    g.drawLine(500, 60, 523, 60);
    g.drawString("二分法", 525, 65);
    g.setColor(Color.red);
    g.drawLine(500, 80, 523, 80);
    g.drawString("牛顿法", 525, 85);
    g.setColor(Color.green);
    g.drawLine(500, 100, 523, 100);
    g.drawString("弦截法", 525, 105);
    if (choosea) {
      g.setColor(Color.black);
      int m = 50, n = 350;
      double a = 0.005, j;
      for (int k = 50; k < 700; k++) {
        j = f(a) * 140;
        g.drawLine(m, n, k, 350 - (int) j);
        m = k;
        n = 350 - (int) j;
        a += 0.005;
      }
    }
    if (chooseb) {
      g.setColor(Color.blue);
      double a=1,b=2,y0,x=0.0,y=0.0,i,j;
      y0=a-2*Math.sin(a);
      while(b-a>=error){
        x=(a+b)/2;y=f(x);i=50+200*x;j=140*y;
        try{
        Thread.sleep(200);//延迟
        }catch(InterruptedException e){}
        g.drawLine((int)i,350,(int)i,350-(int)j);
        if(y*y0>0)
          a=x;
        else
          b=x;
      }
      String T=new String();
      T="x="+T.valueOf(x);
      g.drawString(T,300,500);
      T="f(x)="+T.valueOf(f(x));
      g.drawString(T,500,500);
    }
    if(choosec){
      g.setColor(Color.red);
      int N=20,k,p=0;
      double x0=2.8,x1;
      String T=new String();
W1:   for(k=0;k<N;k++){
        if(fdao(x0)==0){
          g.drawString("奇异方程",300, 500);
          break W1;
        }
        else{
          x1 = x0 - f(x0) / fdao(x0);
          int i=(int)(350-140*f(x0));
          while(i<345){
            try {
              Thread.sleep(100); //延迟
            }
            catch (InterruptedException e) {}
            double m=(50 + x0 * 200);
            g.drawLine( (int) m, (int)i, (int) m,(int) (i+5));
            i+=10;
         }
          if(p==0){
            g.drawLine( (int) (50 + x0 * 200), 350, (int) (50 + x0 * 200), 345);
            p=1;
          }
          g.drawLine( (int) (50 + x0 * 200), (int) (350 - 140 * f(x0)),(int) (50 + x1 * 200), 350);
          if(Math.abs(x1-x0)>=error){
            x0 = x1;
            }
          else{
            T="x1="+T.valueOf(x1);
            g.drawString(T,300,500);
            T="f(x1)="+T.valueOf(f(x1));
            g.drawString(T,500,500);break W1;
          }
        }
      }
      if(k==20){
        g.drawString("迭代失败!(N=20)",300,500);
      }
    }
    if(choosed){
      g.setColor(Color.green);
      String T=new String();
      int N=20,p=0,k;
      double x0=2.8,x1=2.5,x2;
 W1:  for(k=1;k<=N;k++){
        x2=x1-(f(x1)*(x1-x0))/(f(x1)-f(x0));
        int i=(int)(350-f(x0)*140);
        while(i<345){
            try {
              Thread.sleep(100); //延迟
            }
            catch (InterruptedException e) {}
            g.drawLine( (int) (50 + x0 * 200), (int)i, (int) (50 + x0 * 200),(int) (i+5));
            i+=10;
         }
         if(p==0){
            g.drawLine( (int) (50 + x0 * 200), 350, (int) (50 + x0 * 200), 345);
            p-=0.5;
          }

         g.drawLine( (int) (50 + x0 * 200), (int) (350 - 140 * f(x0)),
                     (int) (50 + x1* 200), (int)(350-f(x1)*140));
         g.drawLine( (int) (50 + x1 * 200), (int) (350 - 140 * f(x1)),
                     (int) (50 + x2* 200), 350);
         if(Math.abs(x2-x1)>=error){
          x0=x1;x1=x2;
        }
        else{
          T="x2="+T.valueOf(x2);
          g.drawString(T,300,500);
          T="f(x2)="+T.valueOf(f(x2));
          g.drawString(T,500,500);

          break W1;
        }
      }
      if(k==20){
        g.drawString("sytgsdif",300,500);
      }
    }
   }
 }