example4_1.java

清华大学2002年出版的《科学与工程数值计算算法Java》配套源码

import java.applet.*;
import java.awt.*;

public class Example4_1 extends Applet
{ public static double f(double x)
  {double y;
   y=x-Math.cos(x);
   return y;
  }

  public static double half(double a,double b,double eps)
  {double ya,yb,yc,c=0;
   ya=f(a);yb=f(b);
   while(Math.abs(b-a)>eps)
   {c=(a+b)/2;yc=f(c);
    if(Math.abs(yc)<eps)break;
    else if(ya*yc<0){b=c;yb=yc;}
    else {a=c;ya=yc;}
    }
    return c;
   }

  public void paint(Graphics g)
 {double a=0,b=Math.PI/2,c=0,eps=1e-8;
  c=half(a,b,eps);
  g.drawString("方程在区间(0,PI/2)中的根为"+c,10,20);
 }

}