1、package d7_8;import java.util.Arrays;public class Zuoye_9 {public static void main(String[] args) {long []arr={};long sum=0;for(int i=0;i<10;i++){arr=Arrays.copyOf(arr, arr.length+1);arr[i]=(long) (Math.pow(10, i+1)-1);sum+=arr[i]; if(i==9){ System.out.print(arr[i]); }else{ System.out.print(arr[i]+"+"); } }System.out.print("="+sum);}}
3、Scanner sc=new Scanner(System.in);System.out.println("请输入大于等于2的整数：");double sum = 0;int j=sc.nextInt();for(int i=1;i<=j;i++){double k=(double) i;sum+=1/k; if(i==j){ System.out.println("1"+"/"+i+"="+sum); }else{ System.out.print("1"+"/"+i+"+"); }}}}
5、九九乘法表：
