Java: Viết chương trình Giải phương trình bậc 2.

import java.io.*;

public class Gptb2{

        public static void main(String args[]){

               InputStreamReader isr = new InputStreamReader(System.in);

               BufferedReader br = new BufferedReader(isr);

               try{

                       System.out.println("Nhap gia tri a");

                       String stra = br.readLine();

                       float a = Float.valueOf(stra).floatValue();

                      

                       System.out.println("Nhap gia tri b");

                       String strb = br.readLine();

                       float b = Float.valueOf(strb).floatValue();

                      

                       System.out.println("Nhap gia tri c");

                       String strc = br.readLine();

                       float c = Float.valueOf(strc).floatValue();

                       float delta = b*b - 4*a*c;

                       if(a==0)

                              if(b==0)

                                    if(c==0){

                                                System.out.print("PT co vo so nghiem");

                                    }

                                    else{

                                                System.out.print("PT vo nghiem");

                                    }

                              else{

                                    System.out.println("PT co nghiem duy nhat: " +c/b);

                              }

                       else{

                              if(delta<0){

                                    System.out.println("PT vo nghiem");

                              }

                              else if(delta>0){

                                    float x1 = (float)(-b + Math.sqrt(delta))/(2*a);

                                    float x2 = (float)(-b - Math.sqrt(delta))/(2*a);

                                    System.out.println("PT co 2 nghiem: x1= " +x1 + " va " +x2);

                              }

                              else{

                                    float x = (float)(-b)/(2*a);

                                    System.out.println("PT co nghiem kep: " +x);

                              }

                       }                      

               }

               catch(IOException ie){

                       System.out.println("Error: " +ie);

               }

        }

}