import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class JButton_test extends JFrame implements ActionListener {
   JButton jButton1 = new JButton("   ");
    JTextField jText_number1 = new JTextField();
    JLabel jLabel1 = new JLabel("һ");
    JLabel jLabel2 = new JLabel("");
    JLabel jLabel3 = new JLabel();
    public JButton_test() {
        setLayout(null);
        jButton1.setBounds(80, 85, 83, 25);
        jButton1.addActionListener(this);
        jLabel3.setBounds(96, 52, 96, 27);
        jLabel2.setBounds(44, 56, 50, 22);
        jLabel1.setBounds(15, 19, 99, 26);
        jText_number1.setBounds(123, 14, 83, 32);
        setTitle("ƽ");
        add(jLabel1);
        add(jText_number1);
        add(jLabel2);
        add(jButton1);
       add(jLabel3);
    }
    public void actionPerformed(ActionEvent e) {
        double number = 0;
        try {
         number = Double.valueOf(jText_number1.getText()).doubleValue();
           jLabel3.setText("" + Math.sqrt(number));
           } catch (NumberFormatException event) {
                   jLabel3.setText("ַ");
           } 
  }
    public static void main(String args[]) {
           JButton_test ta = new JButton_test();
           ta.setBounds(200, 200, 250, 150);
           ta.validate();
           ta.setVisible(true);
    }
}
