I try to solve this problem, and i tried to find some bugs in the code, i think that i get WA for some detail that i miss in the output, can anyone help me please.
import java.text.DecimalFormat; 
import java.math.*;
import java.util.*;
import java.io.*;
class Main
{
	public Main ()
	{
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		StringBuffer out = new StringBuffer();
		try
		{
			//BufferedReader in = new BufferedReader(new FileReader("in.txt"));
			DecimalFormat salida = new DecimalFormat("0.000"); 
			String pnts="";
			Point pt1 = null;
			Point pt2 = null;
			Point pt3 = null;
			while((pnts=in.readLine())!=null)
			{
				StringTokenizer str = new StringTokenizer(pnts);
				pt1=new Point(str);
				pt2=new Point(str);
				pt3=new Point(str);
				double yDelta_a= pt2.y - pt1.y;
				double xDelta_a= pt2.x - pt1.x;
				double yDelta_b= pt3.y - pt2.y;
				double xDelta_b= pt3.x - pt2.x;
				double x=0.0;
				double y=0.0;
				double aSlope=yDelta_a/xDelta_a; 
				if(xDelta_a==0.0||yDelta_a==0.0)aSlope=1;
				double bSlope=yDelta_b/xDelta_b;
				if(xDelta_b==0.0||yDelta_b==0.0)bSlope=1;
				x= (aSlope*bSlope*(pt1.y - pt3.y) + bSlope*(pt1.x + pt2 .x)- aSlope*(pt2.x+pt3.x) )/(2* (bSlope-aSlope) );
				y = -1*(x - (pt1.x+pt2.x)/2)/aSlope +  (pt1.y+pt2.y)/2;	
				double r = Math.sqrt((Math.pow(pt1.y-y,2))+(Math.pow(pt1.x-x,2)));
				String sx=salida.format(x*-1);
				sx=qs(sx,true);
				if(x==0)
					sx="x^2";
				else
				{
					sx="(x "+sx+")^2";
				}
				String sy=salida.format(y*-1);
				sy=qs(sy,true);
				if(y==0)
					sy="y^2";
				else
				{
					sy="(y "+sy+")^2";
				}
				sy="+ "+sy;
				String sr=salida.format(r);
				sr=qs(sr,false);
				out.append( sx+" "+sy+" = "+sr+"^2\n");
				String sd = salida.format(2*x*-1);
				sd = qs(sd,true);
				if(2*x*-1==0)
					sd="";
				else
				{
					sd=sd+"x ";
				}
				String se = salida.format(2*y*-1);
				se = qs(se,true);
				if(2*y*-1==0)
					se="";
				else
				{
					se=se+"y ";
				}
				double f =((Math.pow(2*x,2)+Math.pow(2*y,2)-(4*(r*r)))/-4)*-1;
				String sf = salida.format(f);
				sf = qs(sf,true);
				if(f==0)
					sf="";
				out.append("x^2 + y^2 "+sd+se+sf+" = 0\n\n");				
			}
			System.out.print(out.substring(0,out.length()-1));
		}
		catch(Exception e){};
	}
	public String qs(String s, boolean sm)
	{
		if(s.startsWith("-"))
			s = "- "+s.substring(1,s.length());
		else if(sm)
		{
			s = "+ "+s;
		}
		return s;
	}
	public double m(Point p1,Point p2)
	{
		return ((p2.y-p1.y)/(p2.x-p1.x));
	}
	public static void main(String ar[])
	{
		new Main();	
	}
}
class Point
{
	double x=0.0;
	double y=0.0;
	public Point(StringTokenizer str)
	{
		this.x=new Double(str.nextToken());
		this.y=new Double(str.nextToken());
	}
}