import java.util.Scanner;

//import java.util.Scanner;
class Main {
 
  public static void main(String[] args) {
    // Scanner sc = new Scanner(System.in);

    // System.out.print("请输入数组的长度：");
    // int length = sc.nextInt();

    // int[] arr = new int[length];

    // System.out.println("请输入%d个元素", length);
    // for(int i = 0; i < length; i++) {
    //   arr[i] = sc.nextInt();
    // }
      
    int[] arr = {1, 2, 3};
    String str = intToString(arr);
    System.out.println(str);

    String result = reverseSting("abc");
    System.out.println(result);
  }

  public static String intToString(int[] arr) {
    String result = "[";

    if(arr == null) {
      return "";
    }
    if(arr.length == 0) {
      return  "[]";
    }
    //表示数组不是null，也不是长度为0的
    //遍历数组并把数组拼接成一个字符串
    for(int i = 0; i < arr.length; i++) {
      if(i == arr.length - 1) {
        result = result + arr[i];
      } else {
        result = result + arr[i] + ", ";   
      }
    }
    result = result + "]";

    return result;
  }
  
  //字符串反转
  public static String reverseSting(String str) {
    String result = "";

    for(int i = str.length() - 1; i >= 0; i--) {
      char c = str.charAt(i);
      result = result + c;
    }
    return result;
  }
}