面向对象的第三次pta作业第一题：用类解一元二次方程式

import java.util.Scanner;


public class Main {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner input = new Scanner(System.in);

        double a = Double.parseDouble(input.next());
        double b = Double.parseDouble(input.next());
        double c = Double.parseDouble(input.next());
        
        if(a == 0){
            System.out.println("Wrong Format");
            System.exit(0);
        }
        
        //create a QuadraticEquation object
        QuadraticEquation equation = new QuadraticEquation(a, b, c);
        //get value of b * b - 4 * a * c
        double discriminant = equation.getDiscriminant();
        
        System.out.println("a=" + equation.getA() +
                ",b=" + equation.getB() + 
                ",c=" + equation.getC()+":");

        if (discriminant < 0) {
          System.out.println("The equation has no roots.");
        }
        else if (discriminant == 0)
        {
          System.out.println("The root is " + 
                  String.format("%.2f", equation.getRoot1()));
        }
        else // (discriminant >= 0)
        {
          System.out.println("The roots are " + 
                  String.format("%.2f", equation.getRoot1()) 
            + " and " +  String.format("%.2f", equation.getRoot2()));
        }
    }

}

class QuadraticEquation{    
    private double a;
    private double b;
    private double c;
    public QuadraticEquation() {
        
    }
    public QuadraticEquation(double a,double b,double c) {
        this.a = a;
        this.b = b;
        this.c = c;
    }
    public double getA() {
        return a;
    }
    public double getB() {
        return b;
    }
    public double getC() {
        return c;
    }
    public double getDiscriminant() {
        double d = b*b-4*a*c;
        return d;
    }
    public double getRoot1() {
        return ((-1)*b+Math.sqrt(getDiscriminant()))/2/a;
    }
    public double getRoot2() {
        return ((-1)*b-Math.sqrt(getDiscriminant()))/2/a;
    }

    
}

 

 

啊！学新东西了！！！！！

终于和c不一样了！！！！！！！！

一元二次方程的3.0版本噢~

从单纯地用主函数到加入方法，再到类的运用

虽然这道题不是很难

我没有很大体会到类的意义 

但是我会好好学的！！！！！！！！！！！

太感人了