/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH, 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; and CC Bordeianu, Univ Bucharest, 2007.
   Support by National Science Foundation                              
*/
// Bisection.java: Bisection root finder, crude, but reliable

import java.io.* ;
import java.text.* ;

public class Bisection   {
	     
	public static double f(double x)
		{ return 2*Math.cos(x)-x; }

  public static void main(String[] argv)  {
    double eps = 1e-6;                                   // Precision
    double x, xminus = 0., xplus = 7.;      // Range must contain a 0
    int it, imax = 100;                          // Max no iterations
    System.out.println("Iteration     x              f(x)"); 
    DecimalFormat df = new DecimalFormat("#0.0000000000000000"); 
    DecimalFormat in = new DecimalFormat("#00");  // Column formatted
    for( it=0; it <= imax; it++ )  {
      x = ( xplus + xminus )/2.;
      System.out.println("  "+in.format(it)+"   "+df.format(x)+ 
			                                     "  "+ df.format(f(x))); 
      if ( f(xplus) * f(x) > 0. )  xplus = x;            // Algorithm
      else xminus=x;
      if ( Math.abs(f(x)) < eps) {               // Convergence check
        System.out.println("Root found with precision eps = " + eps);
        break;
		  }
    }
  }
}