2020-12-16（上）

import java.util.Scanner;
public class Prog8{
  public static void main(String[] args){
    System.out.print("求s=a+aa+aaa+aaaa+...的值，请输入a的值：");
    Scanner scan = new Scanner(System.in).useDelimiter("\\s*");//以空格作为分隔符
    int a = scan.nextInt();
    int n = scan.nextInt();
    scan.close();//关闭扫描器
    System.out.println(expressed(2,5)+add(2,5));
  } 
  //求和表达式
  private static String expressed(int a,int n){
    StringBuffer sb = new StringBuffer();
    StringBuffer subSB = new StringBuffer();
    for(int i=1;i<n+1;i++){
      subSB = subSB.append(a);
      sb = sb.append(subSB);
      if(i<n)
        sb = sb.append("+");
    }
    sb.append("=");
    return sb.toString();
  }
  //求和
  private static long add(int a,int n){
    long sum = 0;
    long subSUM = 0;
    for(int i=1;i<n+1;i++){
      subSUM = subSUM*10+a;
      sum = sum+subSUM;
    }
    return sum;
  }
}