Java類求解一元二次方程的根
一元二次方程ax2+bx+c=0,輸入a,b,c三個係數,求解方程,結果有三種情況:兩個實數根、一個實數根、兩個複數根。
/**
* Equation.java
*/
package cn.edu.uibe.oop;
/**
* 計算一元二次方程的根
* @author TongQiang
*
*/
public class Equation {
double a,b,c; //方程的係數
double x1,x2; //兩個根
double r; //實部
double v; //虛部
int type; //0表示一個根,1表示兩個實根,2表示兩個複數的根
public Equation(double a,double b,double c){
this.a = a;
this.b = b;
this.c = c;
}
private double delta(){
return b*b-4*a*c;
}
public void calculate(){
double d = delta();
if(Math.abs(d) < 1E-5){
type = 0;
x1 = -b/(2*a);
x2 = x1;
}else if(d > 0){
type = 1;
x1 = (-b+Math.sqrt(d))/(2*a);
x2 = (-b-Math.sqrt(d))/(2*a);
}else{
type = 2;
r = -b/(2*a);
v = Math.sqrt(-d)/(2*a);
}
}
public void showResult(){
switch(type){
case 0:
System.out.println("方程只有一個實根,x1=x2="+x1);
break;
case 1:
System.out.println("方程有兩個實根,分別是:x1="+x1+"/tx2="+x2);
break;
case 2:
System.out.println("方程有兩個複數根,分別是:"+r+"+"+v+"i,/t"+r+"-"+v+"i");
break;
}
}
public static void main(String[] args) {
Equation eq1 = new Equation(1,2,2);
eq1.calculate();
eq1.showResult();
Equation eq2 = new Equation(1,-2,1);
eq2.calculate();
eq2.showResult();
Equation eq3 = new Equation(1,6,5);
eq3.calculate();
eq3.showResult();
}
}