简单的一次二次三次方程求解-Java

import java.io.IOException; import java.util.Scanner; public class SolveEquation{ void print()throws IOException{char ch='y'; System.out.println("求解几次方程？1：一次 2：二次 3：三次"); Scanner sLine=new Scanner(System.in); int pm=sLine.nextInt(); if(pm==1){ System.out.println("你选择的是一元一次方程:"); SolveEquation.SolveSimpleEquation fc=new SolveEquation().new SolveSimpleEquation(); fc.SolveSimpleEquation(); } else if(pm==2){ System.out.println("你选择的是一元二次方程:"); SolveEquation.SolveQuadraticEquation fc=new SolveEquation().new SolveQuadraticEquation(); fc.SolveQuadraticEquation(); } else if(pm==3){ System.out.println("你选择的是一元三次方程:"); SolveEquation.SolveCubicEquation fc=new SolveEquation().new SolveCubicEquation(); fc.SolveCubicEquation(); } else {print();} System.out.println("你是否想继续:(y/n)"); ch=(char)System.in.read(); System.in.skip(2); if(ch=='y')print(); else if(ch=='n'){System.out.println("Good luck!");} else print(); } public static void main (String args[]) throws IOException{ SolveEquation se=new SolveEquation(); se.print(); } interface I1{void SolveCubicEquation();} interface I2{void SolveQuadraticEquation();} interface I3{void SolveSimpleEquation();} class SolveCubicEquation implements I1{ public void SolveCubicEquation(){ System.out.println("请输入形如一元三次方程mx^3+nx^2+tx+s=0的四个系数"); Scanner sce=new Scanner(System.in); double m=sce.nextDouble(); double n=sce.nextDouble(); double t=sce.nextDouble(); double s=sce.nextDouble(); if(m==0)System.out.print("输入错误!"); else { double a=n/m; double b=t/m; double c=s/m; double q=(a*a-3*b)/9; double r=(2*a*a*a-9*a*b+27*c)/54; if(r*r<q*q*q){ System.out.println("此方程有三个解:"); t=Math.acos(r/Math.sqrt(q*q*q)); double x1=-2*Math.sqrt(q)*Math.cos(t/3)-a/3; double x2=-2*Math.sqrt(q)*Math.cos((t+2*Math.PI)/3)-a/3; double x3=-2*Math.sqrt(q)*Math.cos((t-2*Math.PI)/3)-a/3; System.out.println("x1="+x1+","+"x2="+x2+","+"x3="+x3); } else{ System.out.println("此方程只有一个解:"); int sgn=(r>=0)?1:-1; double u=-sgn*Math.pow((Math.abs(r)+Math.sqrt(r*r-q*q*q)),1./3); double v=(u!=0)?q/u:0; double x1=u+v-a/3; System.out.println("x="+x1); } } } } class SolveQuadraticEquation implements I2{ public void SolveQuadraticEquation(){ System.out.println("请输入形如一元二次方程ax^2+bx+c=0的三个系数"); Scanner sce=new Scanner(System.in); double a=sce.nextDouble(); double b=sce.nextDouble(); double c=sce.nextDouble(); if(a==0)System.out.print("输入错误!"); else { double d=b*b-4*a*c; if(d>0){ double x1=(-b+Math.sqrt(d))/2*a; double x2=(-b+Math.sqrt(d))/2*a; System.out.println("有两个实根x1="+x1+","+"x2="+x2); } else if(d==0){ System.out.println("有一个实根"+(-b/2*a)); } else if(d<0){ double Re=-b/(2*a); double Im=Math.sqrt(-d)/(2*a); System.out.println("实部="+Re+" "+"虚部="+Im); } } } } class SolveSimpleEquation implements I3{ public void SolveSimpleEquation(){ System.out.println("请输入形如一元一次方程ax+b=0的两个系数"); Scanner sce=new Scanner(System.in); double a=sce.nextDouble(); double b=sce.nextDouble(); if(a==0)System.out.print("输入错误!"); else { System.out.println("方程的根是x="+(-b/a)); } } } }