编译通过，但是程序运行到b.paixv(a)就停止了。

import java.util.Scanner;
import java.util.Arrays;
public class project3_5{
static void input(double a[]){
Scanner in = new Scanner(System.in);
for(int i=0;i<a.length;i++){
a[i] = in.nextDouble();
}
}
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int n = in.nextInt();
double [] a = new double[n];
System.out.println("qing shu ru mei ge shan ping de hua fe:");
input(a);
BigAndSmall b  = new BigAndSmall();
double sumMoney = 0;
b.paixv(a);
sumMoney = b.sum(a);
MartDemo yang = new MartDemo();
yang.ff(sumMoney);

}
}

public class MartDemo{
 public double price  = 0;
 public double ff(double sumMoney){
if(sumMoney>=1000)
{
sumMoney*=0.8;
this.price = 200;
}
else if(sumMoney>=500)
{
sumMoney *=0.85;
this.price = 100;
}
else if(sumMoney>=300)
{
sumMoney*=0.9;
this.price = 70;
}
else
sumMoney*=0.95;
System.out.printf("shi ji hua fe:%.2lf",sumMoney);
System.out.printf("huo de de ge wu quan jin e:%lf",this.price);
return sumMoney;
}
}

import java.util.Arrays;
import java.util.Scanner;
import java.util.Formatter;
public class BigAndSmall{
  public void paixv(double a[]){
    int i,j;
        for(i=0;i<a.length-1;i++)
          {
              int min=i;
              double t ;
              for( j=i+1;j<a.length;j++)
               if(a[min]>a[j])
               {
                   min=j;
               }
               if(min!=i)
               {t=a[i];a[i]=a[min]; a[min]=t;}
          }
          System.out.println("pai xv jie guo ru xia:");
          System.out.println(Arrays.toString(a));
}
  public double sum(double a[]){
double s = 0;
for(int i=0;i<a.length;i++)
s+=a[i];
System.out.printf("yong fu zong hua fu %lf",s);
return s;
}
}