//计算类
public class Caculate {
double a1;
int n;
double d;
double an;
public Caculate(double a1,double d,int n) {
this.a1=a1;
this.d=d;
this.n=n;
}
public double getN()
{
an=a1+(n-1)*d;
return an;
}
public static void main(String[] args) {
//初始化参数为首项,公差和要求项的编号
Caculate c = new Caculate(5.50, 7.0, 20);
System.out.println("等差数列的第20项为:"+c.getN());
}
}
运行如下: