jifen.java

计算方法课

import java.awt.*;
import java.applet.*;
import java.awt.event.*;
import java.lang.*;
public class jifen extends Applet implements ActionListener{
  double a=0.0001,b=6,error=0.0001;
  Button A, B,C;
  boolean choosea, chooseb,choosec;

  public void init() {
    A = new Button("龙贝格算法");
    B = new Button("变步长梯形算法");
    C=new Button("f(x)曲线");
    add(C);add(A);add(B);
    A.addActionListener(this);
    B.addActionListener(this);
    C.addActionListener(this);
    }
  public void actionPerformed(ActionEvent ae) {
    String str = ae.getActionCommand();
    if (str.equals("龙贝格算法")) {
      choosea = true;chooseb=false;choosec = false;
      repaint();
    }
    if(str.equals("变步长梯形算法")){
        chooseb=true;choosea = false;choosec = false;
        repaint();
    }
    if(str.equals("f(x)曲线")){
      choosec = true;choosea=false;chooseb=false;
      repaint();
    }
  }

  public void paint(Graphics g) { //绘图
    g.drawLine(30, 350, 30, 30);
    g.drawLine(30, 250, 400, 250);
    g.drawLine(30, 30, 34, 39);
    g.drawLine(30, 30, 26, 39);
    g.drawLine(400, 250, 395, 245);
    g.drawLine(400, 250, 395, 255);
    for(int i=1;i<7;i++)
    	g.drawLine(30+i*50,250,30+i*50,245);//比例为1：50
    g.drawString("1",78,265);g.drawString("2",128,265);
    g.drawString("3",178,265);g.drawString("4",228,265);
    g.drawString("5",278,265);g.drawString("6",328,265);
    g.drawLine(30,300,35,300);g.drawString("-0.5",8,305);
    g.drawLine(30,200,35,200);g.drawString("0.5",10,205);
    g.drawLine(30,150,35,150);g.drawString("1",20,155);
    g.drawString("x", 405, 260);
    g.drawString("y", 20, 32);
    g.drawString("0", 20, 255);
    g.drawString("a=0,b=6,误差为:0.0001",50,380);

    g.setColor(Color.green);
    g.drawLine(400, 40, 423, 40);
    g.drawString("f(x)曲线", 425, 45);
    g.setColor(Color.blue);
    g.drawLine(400, 60, 423, 60);
    g.drawString("龙贝格曲线", 425, 65);
    g.setColor(Color.red);
    g.drawLine(400, 80, 423, 80);
    g.drawString("变步长梯形曲线", 425, 85);
    if(choosec){
      g.setColor(Color.green);
      g.drawString("y=sin(x)/x",150,200);
      int x=30,y=150;double a=0.02;
      for(int i=31;i<=330;i++){
      	double j=f(a)*100;
        g.drawLine(x,y,i,250-(int)j);
        try{
          Thread.sleep(5);
        }catch(InterruptedException e){}
        x=i;y=250-(int)j;
        a+=0.02;
      }

    }
    if (choosea) {
      g.setColor(Color.blue);
      int x=30,y=150;
      double j,a=0.02;
      for(int i=31;i<=330;i++){
      	j=f(a)*100;
      	g.drawLine(x,y,i,250-(int)j);
        try{
          Thread.sleep(5);
        }catch(InterruptedException e){}

        if((boolean)(i%20==0))
        g.drawLine(x,y,x,250);
        x=i;y=250-(int)j;
        a+=0.02;
      }
      g.drawString("龙贝格算法值为:",50,350);
      String T=new String();
      g.drawString(T.valueOf(longbg()),150,350);
    }
    if (chooseb) {
      g.setColor(Color.red);
      int x=30,y=150;
      double j,a=0.02;
      for(int i=31;i<=330;i++){
      	j=f(a)*100;
      	g.drawLine(x,y,i,250-(int)j);
        try{
            Thread.sleep(5);
        }catch(InterruptedException e){}

        if((boolean)(i%10==0))
        g.drawLine(x,y,x,250);

        x=i;y=250-(int)j;
        a+=0.02;
      }
      g.drawString("变步长算法值为:",300,350);
      String T=new String();
      g.drawString(T.valueOf(bianbc()),400,350);
      }
  }
 public double f(double x){
   return Math.sin(x)/x;
 }

 public double longbg(){//龙贝格算法
   double h, k, s, x, s1 = 0.0, s2, c1 = 0.0, c2, T1, T2, R1 = 0.0, R2;
   h = b - a;
   T1 = (f(a) + f(b)) * h / 2;
   k = 1;
   W1:while (true) {
     s = 0;
     x = a + h / 2;
     do {
       s = s + f(x);
       x = x + h;
     }
     while (x < b);
     T2 = (T1 + h * s) / 2;
     s2 = T2 + (T2 - T1) / 3;
     if (k == 1) {
       k = k + 1;
       h = h / 2;
       T1 = T2;
       s1 = s2;
       continue W1;
     }
     else
       c2 = s2 + (s2 - s1) / 15;
     if (k == 2) {
       c1 = c2;
       k = k + 1;
       h = h / 2;
       T1 = T2;
       s1 = s2;
       continue W1;
     }
     else
       R2 = c2 + (c2 - c1) / 63;
     if (k == 3) {
       R1 = R2;
       c1 = c2;
       k = k + 1;
       h = h / 2;
       T1 = T2;
       s1 = s2;
       continue W1;
     }
     else if (Math.abs(R2 - R1) >= error) {
       R1 = R2;
       c1 = c2;
       k = k + 1;
       h = h / 2;
       T1 = T2;
       s1 = s2;
       continue W1;
     }
     else
       break W1;
   }
   return(R2);
 }
  public double bianbc(){//变步长算法
    double h,T1,T2,S,x;
    h=b-a;
    T1=((Math.sin(a))/a+(Math.sin(b))/b)*h/2;
    W1:while(true){
    S=0;
     x=a+h/2;
     do{
     S = S + Math.sin(x)/x;;
     x = x + h;
     }while(x<b);
     T2=(T1+h*S)/2;
     if(Math.abs(T2-T1)>=error){
     h = h / 2;
     T1 = T2;
     }
     else
     break W1;
     }
     return(T2);
   }

}