io操作过程，有时候，我们是需要重新创建文件，有时候只要在文件末尾追加内容，就可以，那么如何追加呢，给出3种方法：

1. import java.io.BufferedWriter;                                                       
2. import java.io.FileOutputStream;                                                     
3. import java.io.FileWriter;                                                           
4. import java.io.IOException;                                                          
5. import java.io.OutputStreamWriter;                                                   
6. import java.io.RandomAccessFile;                                                     
7.                                                                                      
8.                                                                                      
9. public class WriteStreamAppend {                                                     
10.                                                                                      
11.     public static void method1(String file, String conent) {                         
12.         BufferedWriter out = null;                                                   
13.         try {                                                                        
14.              //FileOutputStream构造函数中的第二个参数true表示以追加形式写文件 
15.              out = new BufferedWriter(new OutputStreamWriter(                        
16.                     new FileOutputStream(file, true)));                              
17.              out.write(conent);                                                      
18.          } catch (Exception e) {                                                     
19.              e.printStackTrace();                                                    
20.          } finally {                                                                 
21.             try {                                                                    
22.                  out.close();                                                        
23.              } catch (IOException e) {                                               
24.                  e.printStackTrace();                                                
25.              }                                                                       
26.          }                                                                           
27.      }                                                                               
28.                                                                                      
29.                                                                                      
30.     public static void method2(String fileName, String content) {                    
31.         try {                                                                        
32.             // 打开一个写文件器，构造函数中的第二个参数true表示以追加形式写文件      
33.              FileWriter writer = new FileWriter(fileName, true);                     
34.              writer.write(content);                                                  
35.              writer.close();                                                         
36.          } catch (IOException e) {                                                   
37.              e.printStackTrace();                                                    
38.          }                                                                           
39.      }                                                                               
40.                                                                                      
41.                                                                                      
42.     public static void method3(String fileName, String content) {                    
43.         try {                                                                        
44.             // 打开一个随机访问文件流，按读写方式                                    
45.              RandomAccessFile randomFile = new RandomAccessFile(fileName, "rw");     
46.             // 文件长度，字节数                                                      
47.             long fileLength = randomFile.length();                                   
48.             // 将写文件指针移到文件尾。                                              
49.              randomFile.seek(fileLength);                                            
50.              randomFile.writeBytes(content);                                         
51.              randomFile.close();                                                     
52.          } catch (IOException e) {                                                   
53.              e.printStackTrace();                                                    
54.          }                                                                           
55.      }                                                                               
56.                                                                                      
57.     public static void main(String[] args) {                                         
58.          System.out.println("start");                                                
59.          method1("c:/test.txt", "追加到文件的末尾");                                 
60.          System.out.println("end");                                                  
61.      }
62.                    

参考文章：https://blog.csdn.net/stefshawn/article/details/7303124