java IO写入文件效率——几种方法比较

总结：

如果按字符和字节来分类，除方法1和2，其余都是按字符写入文件，字符写入一般比字节快；看java API可知，FileWriter的父类就是OutputStreamWriter，他俩都是实现Writer类，从这点上来说，方法4和6几乎没区别，时间有些微的差别，但内部机制是一样的，而且方法6较简单，定义变量稍，以前总用方法4，看来以后得改变下了。

测试写入类



/**
  * 测试结果
  *
  * 1.file's long:16kb
  *
  fileWrite's time----------36
  outputStreamTest's time----------167
  bufferedOutputTest's time----------17
  bufferedWriteTest's time----------14
  bufferedWrite And FileWriterTest's time----------9
  bufferedWrite And BufferedOutputStreamTest's time----------12
  *
  * 2.file's long:1600kb
  fileWrite's time----------69
  outputStreamTest's time----------1282
  bufferedOutputTest's time----------68
  bufferedWriteTest's time----------40
  bufferedWrite And FileWriterTest's time----------52
  bufferedWrite And BufferedOutputStreamTest's time----------37
  *
  * 3.file's long:16000kb
  fileWrite's time----------555
  outputStreamTest's time----------12448
  bufferedOutputTest's time----------599
  bufferedWriteTest's time----------346
  bufferedWrite And FileWriterTest's time----------316
  bufferedWrite And BufferedOutputStreamTest's time----------358
   4.file's long:160000kb
 
  fileWrite's time----------5203
  outputStreamTest's time----------127182
  bufferedOutputTest's time----------5972
  bufferedWriteTest's time----------3445        最优
  bufferedWrite And FileWriterTest's time----------5904
  bufferedWrite And BufferedOutputStreamTest's time----------5353
 
 
  5.file's long:1600000kb
 
  fileWrite's time----------50416
  outputStreamTest's time----------1303242
  bufferedOutputTest's time----------60931
  bufferedWriteTest's time----------46697
  bufferedWrite And FileWriterTest's time----------48710
  bufferedWrite And BufferedOutputStreamTest's time----------64354
  */

public static void main(String[] args) {

  String str = "abcdefghiJKLMN！";
  int count = 1000000;
  TestOutputStream t = new TestOutputStream();
  long start = System.currentTimeMillis();
  t.fileWriteTest(count, str);
  long end = System.currentTimeMillis();
  System.out.println("fileWrite's time---------" + (start - end));

  start = System.currentTimeMillis();
  t.outputStreamTest(count, str);
  end = System.currentTimeMillis();
  System.out.println("outputStreamTest's time---------" + (start - end));
 
  start = System.currentTimeMillis();
  t.bufferedOutputTest(count, str);
  end = System.currentTimeMillis();
  System.out
    .println("bufferedOutputTest's time---------" + (start - end));
 
  start = System.currentTimeMillis();
  t.bufferedWriteTest(count, str);
  end = System.currentTimeMillis();
  System.out.println("bufferedWriteTest's time---------" + (start - end));
 
  start = System.currentTimeMillis();
  t.bufferedWriteAndFileWriterTest(count, str);
  end = System.currentTimeMillis();
  System.out.println("bufferedWrite And FileWriterTest's time---------" + (start - end));
 
  start = System.currentTimeMillis();
  t.bufferedWriteAndBufferedOutputStreamTest(count, str);
  end = System.currentTimeMillis();
  System.out.println("bufferedWrite And BufferedOutputStreamTest's time---------" + (start - end));
  
 
}



/**
  *1 按字节写入 FileOutputStream
  *
  * @param count 写入循环次数
  * @param str 写入字符串
  */
public void outputStreamTest(int count, String str) {
  File f = new File("f:test1.txt");
  OutputStream os = null;
  try {
   os = new FileOutputStream(f);
   for (int i = 0; i < count; i++) {
    os.write(str.getBytes());
   }
   os.flush();
   System.out.println("file's long:" + f.length());
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   try {
    os.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
}


  /**
  *2 按字节缓冲写入 BufferedOutputStream
  *
  * @param count 写入循环次数
  * @param str 写入字符串
  */
public void bufferedOutputTest(int count, String str) {
  File f = new File("f:test2.txt");
  BufferedOutputStream bos = null;
  try {
   OutputStream os = new FileOutputStream(f);
   bos = new BufferedOutputStream(os);
   for (int i = 0; i < count; i++) {
    bos.write(str.getBytes());
   }
   bos.flush();
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   try {
    bos.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
}



  /**
  *3 按字符写入 FileWriter
  *
  * @param count 写入循环次数
  * @param str 写入字符串
  */
public void fileWriteTest(int count, String str) {
  File f = new File("f:test.txt");
  Writer writer = null;
  try {
   writer = new FileWriter(f);
   for (int i = 0; i < count; i++) {
    writer.write(str);
   }
   writer.flush();
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   try {
    writer.close();
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
}


  /**
  *4 按字符缓冲写入 BufferedWriter
  *
  * @param count 写入循环次数
  * @param str 写入字符串
  */
public void bufferedWriteTest(int count, String str) {
  File f = new File("f:test3.txt");
  OutputStreamWriter writer = null;
  BufferedWriter bw = null;
  try {
   OutputStream os = new FileOutputStream(f);
   writer = new OutputStreamWriter(os);
   bw = new BufferedWriter(writer);
   for (int i = 0; i < count; i++) {
    bw.write(str);
   }
   bw.flush();
   if(f.exists()){
    f.delete();
   }
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   try {
    bw.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
}


 
/**
  *5 按字符缓冲写入 BufferedWriter and BufferedOutputStream
  *
  * @param count 写入循环次数
  * @param str 写入字符串
  */
public void bufferedWriteAndBufferedOutputStreamTest(int count, String str) {
  File f = new File("f:test4.txt");
  BufferedOutputStream bos=null;
  OutputStreamWriter writer = null;
  BufferedWriter bw = null;
  try {
   OutputStream os = new FileOutputStream(f);
   bos=new BufferedOutputStream(os);
   writer = new OutputStreamWriter(bos);
   bw = new BufferedWriter(writer);
   for (int i = 0; i < count; i++) {
    bw.write(str);
   }
   bw.flush();
   if(f.exists()){
    f.delete();
    System.out.println("delete---");
   }
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   try {
    bw.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
}

  /**
  *6 按字符缓冲写入 BufferedWriter and FileWriter
  *
  * @param count 写入循环次数
  * @param str 写入字符串
  */
public void bufferedWriteAndFileWriterTest(int count, String str) {
  File f = new File("f:test5.txt");
  FileWriter fw=null;
  BufferedWriter bw = null;
  try {
   fw=new FileWriter(f);
   bw = new BufferedWriter(fw);
   for (int i = 0; i < count; i++) {
    bw.write(str);
   }
   bw.flush();
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   try {
    bw.close();
    if(f.exists()){
     f.delete();
    }
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
}