package qiugengongshi;

public class Root {
  
    private double a,b,c,derta;

    public double getFirstA(){
           return a;}
    public void setFirstA(double a){
               this.a=a;
    }
   
    public double getSecondB(){
           return b;}
    public void setSecondB(double b){
               this.b=b;}
  
   
    public double getThirdC(){
           return c;}
    public void setThirdC(double c){
            this.c=c;}
            
               
        //怎么在这写一个判断derta的值，并且返回给Main类
        public double calculateRoot1(double a,double b, double c){
            
            return (-b+Math.sqrt(b*b-4*a*c))/(2*a);}
            
            public double calculateRoot2(double a,double b ,double c){
            return (-b-Math.sqrt(b*b-4*a*c))/(2*a);
        }
        
    }

目测get、set方法错了
public double getA() {
        return a;
    }

    public void setA(double a) {
        this.a = a;
    }

    public double getB() {
        return b;
    }

    public void setB(double b) {
        this.b = b;
    }

    public double getC() {
        return c;
    }

    public void setC(double c) {
        this.c = c;
    }

         //怎么在这写一个判断derta的值，并且返回给Main类
        public double calculateRoot1(double a,double b, double c){
             return (-b+Math.sqrt(b*b-4*a*c))/(2*a);
        }
            
         public double calculateRoot2(double a,double b ,double c){
             return (-b-Math.sqrt(b*b-4*a*c))/(2*a);
         }
您这是两个不同的方法，main主函数，调用哪个就返回方法的计算结果，用判断吗？要判断你就要两个合成一个方法，里面根据判断条件返回...

九九也开始学java了~