Exercise03_01

 import javax.swing.JOptionPane;
 public class TheDirection {
     public static void main(String[] args){
         double a,b,c,t,r1,r2;
         String number;
         int messageType=JOptionPane.INFORMATION_MESSAGE;
         number=JOptionPane.showInputDialog(null,"输入a");
         a=Double.parseDouble(number);
         number=JOptionPane.showInputDialog(null,"输入b");
         b=Double.parseDouble(number);
         number=JOptionPane.showInputDialog(null,"输入c");
         c=Double.parseDouble(number);
         t = b*b-4*a*c;
         if(t>0){
             r1 = (-b+Math.pow(t,0.5))/(2*a);
             r2 = (-b-Math.pow(t,0.5))/(2*a);
             String message="The equation has two roots " + r1 + " and "+ r2;
             JOptionPane.showMessageDialog(null,message,"result",messageType);
         }
         else if(t==0){
             r1 = (-b+Math.pow(t,0.5))/(2*a);
             String message="The equation has one roots " + r1;
             JOptionPane.showMessageDialog(null,message,"result",messageType);
         }
         else{
             String message="The equation has no real roots ";
             JOptionPane.showMessageDialog(null,message,"result",messageType);
         }

     }
 }