import?java.io.IOException;
import?java.util.Scanner;

public?class?SolveEquation{

void?print（）throws?IOException{char?ch=‘y‘;
????????System.out.println（“求解幾次方程？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（“你選擇的是一元一次方程:“）;
??????SolveEquation.SolveSimpleEquation?fc=new?SolveEquation（）.new?SolveSimpleEquation（）;
??????fc.SolveSimpleEquation（）;
????}
?????else?if（pm==2）{
???????System.out.println（“你選擇的是一元二次方程:“）;
???????SolveEquation.SolveQuadraticEquation?fc=new?SolveEquation（）.new?SolveQuadraticEquation（）;
???????fc.SolveQuadraticEquation（）;
????}
?????else?if（pm==3）{
???????System.out.println（“你選擇的是一元三次方程:“）;
???????SolveEquation.SolveCubicEquation?fc=new?SolveEquation（）.new?SolveCubicEquation（）;
???????fc.SolveCubicEquation（）;
?????}
??????else?{print（）;}
??????System.out.println（“你是否想繼續(xù):（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（“請輸入形如一元三次方程mx^3+nx^2+tx+s=0的四個(gè)系數(shù)“）;
????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（“輸入錯(cuò)誤!“）;
???????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??????????????????????System.out.println（“此方程有三個(gè)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（“此方程只有一個(gè)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（“請輸入形如一元二次方程ax^2+bx+c=0的三個(gè)

?屬性????????????大小?????日期????時(shí)間???名稱
-----------?---------??----------?-----??----
?????文件?????????307??2011-05-09?15:29??equation\.classpath
?????文件?????????384??2011-05-09?15:29??equation\.project
?????文件?????????634??2011-05-09?15:29??equation\.settings\org.eclipse.jdt.core.prefs
?????文件?????????200??2011-05-09?17:06??equation\bin\SolveEquation$I1.class
?????文件?????????204??2011-05-09?17:06??equation\bin\SolveEquation$I2.class
?????文件?????????201??2011-05-09?17:06??equation\bin\SolveEquation$I3.class
?????文件????????2206??2011-05-09?17:06??equation\bin\SolveEquation$SolveCubicEquation.class
?????文件????????1759??2011-05-09?17:06??equation\bin\SolveEquation$SolveQuadraticEquation.class
?????文件????????1236??2011-05-09?17:06??equation\bin\SolveEquation$SolveSimpleEquation.class
?????文件????????2102??2011-05-09?17:06??equation\bin\SolveEquation.class
?????文件????????4492??2011-05-09?17:06??equation\src\SolveEquation.java