1 //需求： 编写一个数组 的工具类
 2 class MyArrays<T> {
 3     public void reverse(T[] arr) {
 4         for (int startIndex = 0, endIndex = arr.length - 1; startIndex < endIndex; startIndex++, endIndex--) {
 5             T temp = arr[startIndex];
 6             arr[startIndex] = arr[endIndex];
 7             arr[endIndex] = temp;
 8         }
 9     }
10 
11     public String toString(T[] arr) {
12         StringBuilder sb = new StringBuilder();
13         for (int i = 0; i < arr.length; i++) {
14             if (i == 0) {
15                 sb.append("[" + arr[i] + ",");
16             } else if (i == arr.length - 1) {
17                 sb.append(arr[i] + "]");
18             } else {
19                 sb.append(arr[i] + ",");
20             }
21         }
22         return sb.toString();
23     }
24 }
25 
26 public class Demo2 {
27     public static void main(String[] args) {
28         Integer[] arr = { 1, 2, 3, 4 };
29         MyArrays<Integer> tool = new MyArrays();
30         tool.reverse(arr);
31         System.out.println("数组的元素为： " + tool.toString(arr));
32 
33         String[] arr2 = { "aaa", "bbb", "ccc" };
34         MyArrays<String> tool2 = new MyArrays();
35         tool2.reverse(arr2);
36         System.out.println("数组的元素为： " + tool2.toString(arr2));
37     }
38 
39 }