/*
ニュートン法による平方根の計算 
*/

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Sqrt extends JFrame implements ActionListener {
	JButton bt1,bt2;
	JTextField tf1,tf2;

	public Sqrt(){
		Container cp =getContentPane();
		cp.setLayout(null);
		JLabel lb1 = new JLabel("x = ");
		JLabel lb2 = new JLabel("sqrt(x) = ");
		lb1.setBounds(5,5,60,25);
		lb2.setBounds(5,40,60,25);
		cp.add(lb1);
		cp.add(lb2);
    tf1 = new JTextField(80);
    tf2 = new JTextField(80);
	 	tf1.setBounds(65,5,220,25);
	 	tf2.setBounds(65,40,220,25);
		cp.add(tf1);
		cp.add(tf2);
		bt1 = new JButton("計　算");
		bt2 = new JButton("終　了");
	 	bt1.setBounds(70,80,80,25);
	 	bt2.setBounds(160,80,80,25);
		bt1.addActionListener(this);
		bt2.addActionListener(this);
		cp.add(bt1);
		cp.add(bt2);
	}
	
	public static void main(String argv[]){
		Sqrt fr = new Sqrt();
		fr.setSize(300,150); 
		fr.setVisible(true);
	}
	
  public void actionPerformed(ActionEvent event) {
    if(event.getSource()==bt1){
  		double x = Double.valueOf(tf1.getText()).doubleValue();
  		if(x<0){
  			tf2.setText("計算不能！");
  		}
  		if(x==0.0){
  			tf2.setText("0.0");
  		}	
  		if(x>0){
  			tf2.setText(Double.toString(sqrt_0(x)));
  		}
  	}
  	if(event.getSource()==bt2){
    	dispose();
    	System.exit(0);
    }
  }
  
  public double sqrt_0 (double xx){
  	double eps = 1.0e-15;
  	double x0;
  	double x1=1.0;
  	do{
  		x0 = x1;
  		x1 =(x0+xx/x0)*0.50;
  	}while(Math.abs(x1-x0)>eps);
  	return x1;
  }
}