java写文件

  1 使用FileWrite写文本文件
  2 
  3 
  4 public static void useFileWriter(String fileName) throws IOException {
  5     File file = new File(fileName);
  6     FileWriter fileWriter = new FileWriter(file);
  7 
  8     fileWriter.write("it is a test");
  9 
 10     fileWriter.close();
 11 }
 12 
 13 
 14 
 15 使用BufferedWrite写文本文件
 16 
 17 
 18 public static void useBufferedWriter(String fileName) throws IOException{
 19     File file = new File(fileName);
 20     BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(fileName));
 21 
 22     bufferedWriter.write("hello bufferedwrite");
 23 
 24     bufferedWriter.flush();
 25     bufferedWriter.close();
 26 }
 27 
 28 
 29 
 30 使用Files写文件,最简单
 31 
 32 
 33 public static void useJdk8(String fileName) throws IOException {
 34     Files.write(Paths.get(fileName), "hello usejdk8".getBytes(), StandardOpenOption.CREATE);
 35 }
 36 
 37 
 38 私用FileOutputStream写文件
 39 
 40 
 41 public static void useFileOutputStream(String fileName) throws IOException{
 42     File file = new File(fileName);
 43 
 44     FileOutputStream fileOutputStream = new FileOutputStream(file);
 45     fileOutputStream.write("hello fileoutputstream".getBytes());
 46 
 47     fileOutputStream.flush();
 48 
 49     fileOutputStream.close();
 50 }
 51 
 52 
 53 
 54 使用BufferedFileOutputStream写文件,速度最快，数据cache在jvm中，容易丢数据
 55 
 56 
 57 public static void useBufferedFileOutputStream(String fileName) {
 58     File file = new File(fileName);
 59 
 60 
 61     BufferedOutputStream bufferedOutputStream = null;
 62     try {
 63         bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(file));
 64 
 65         bufferedOutputStream.write("hello BufferedFileOutputStream".getBytes());
 66 
 67         bufferedOutputStream.flush();
 68     }catch(IOException e) {
 69 
 70 
 71     }finally {
 72         if(bufferedOutputStream!=null) {
 73             try {
 74                 bufferedOutputStream.close();
 75             } catch (IOException e1) {
 76                 //TODO  do something
 77             }
 78         }
 79     }
 80 
 81 }
 82 
 83 
 84 
 85 使用RandomAccessFile写文件，速度最慢,直接刷盘
 86 
 87 
 88 public static void useRandomAccessFile(String fileName) {
 89     RandomAccessFile randomAccessFile = null;
 90 
 91 
 92     try {
 93         randomAccessFile = new RandomAccessFile(fileName, "rw");
 94         randomAccessFile.seek(15); //从第15个byte位置开始写, 原文件的第15个之后的字符会被覆盖一部分
 95         randomAccessFile.write("useRandomAccessFile".getBytes());
 96     } catch (IOException e) {
 97         e.printStackTrace();
 98     }finally {
 99         if(randomAccessFile!=null) {
100             try {
101                 randomAccessFile.close();
102             } catch (IOException e) {
103                 e.printStackTrace();
104             }
105         }
106 
107     }
108 }
109 
110 
111 
112 使用FileChannel写文件
113 
114 
115 public static void useFileChannel(String fileName) {
116 
117     FileChannel fileChannel = null;
118     try {
119         FileChannel channel = new FileOutputStream(fileName).getChannel();
120         channel.write(ByteBuffer.wrap("useFileChannel".getBytes()));
121     } catch (IOException e) {
122         e.printStackTrace();
123     } finally {
124         if(fileChannel!=null) {
125             try {
126                 fileChannel.close();
127             } catch (IOException e) {
128                 e.printStackTrace();
129             }
130         }
131     }
132 }
133 
134 
135 
136 使用MappedByteBuffer写文件,速度快，OS级别内存映射
137 
138 
139 public static void useMappedByteBuffer(String fileName){
140 
141     RandomAccessFile randomAccessFile = null;
142 
143     try {
144         randomAccessFile  = new RandomAccessFile(fileName, "rw");
145         FileChannel fileChannel = randomAccessFile.getChannel();
146 
147 
148         String content = "useMappedByteBuffer";
149 
150         MappedByteBuffer mappedByteBuffer = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, content.getBytes().length);
151 
152         mappedByteBuffer.put(content.getBytes());   //mappedByteBuffer大小不能小于content的字节数
153 
154 
155     } catch (IOException e) {
156         e.printStackTrace();
157     }finally {
158         if(randomAccessFile!=null) {
159             try {
160                 randomAccessFile.close();
161             } catch (IOException e) {
162                 e.printStackTrace();
163             }
164         }
165     }
166 }