1 package demo03;
 2 
 3 public class StringBufferDemo {
 4     public static void main(String[] args) {
 5         func();
 6     }
 7     
 8     public static void func() {
 9         StringBuffer buffer = new StringBuffer();
10         buffer.append("abcd").append(1);
11         System.out.println(buffer);    //abcd1
12         
13         buffer.delete(1, 3);
14         System.out.println(buffer);    //ad1
15         
16         buffer.insert(1, "123");
17         System.out.println(buffer);    //a123d1
18         
19         buffer.replace(1, 4, "jdk");
20         System.out.println(buffer);    //ajdkd1
21         
22         buffer.reverse();
23         System.out.println(buffer);    //1dkdja
24         
25         String s = buffer.toString();
26         System.out.println(s);        //1dkdja
27         
28     }
29 }

 1 package demo03;
 2 
 3 public class StringBufferTest {
 4     //{1,2,3,4,5} => [1,2,3,4,5]
 5     public static void main(String[] args) {
 6         int[] arr = {1,2,3,4,5};
 7         System.out.println(toString(arr));
 8     }
 9     
10     public static String toString(int[] arr) {
11         StringBuffer buffer = new StringBuffer();
12         buffer.append("[");
13         for (int i = 0; i < arr.length; i++) {
14             if (i == arr.length - 1) {
15                 buffer.append(arr[i]).append("]");
16             } else {
17                 buffer.append(arr[i]).append(",");
18             }
19         }
20         
21         return buffer.toString();
22     }
23     
24 }