Java IO写文件效率

写入方法：

　　

/**
 *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();
        }
    }
}

测试写入类：

　　

public static void main(String[] args) {
    String str = "abcdefghiJKLMN！";
    int count = 1000000;
    TestOutputStream t = new TestOutputStream();

    //1.fileWrite's time
    long start = System.currentTimeMillis();
    t.fileWriteTest(count, str);
    long end = System.currentTimeMillis();
    System.out.println("fileWrite's time---------" + (start - end));

    //2.outputStreamTest's time
    start = System.currentTimeMillis();
    t.outputStreamTest(count, str);
    end = System.currentTimeMillis();
    System.out.println("outputStreamTest's time---------" + (start - end));

    //3.bufferedOutputTest's time
    start = System.currentTimeMillis();
    t.bufferedOutputTest(count, str);
    end = System.currentTimeMillis();
    System.out.println("bufferedOutputTest's time---------" + (start - end));

    //4.bufferedWriteTest's time
    start = System.currentTimeMillis();
    t.bufferedWriteTest(count, str);
    end = System.currentTimeMillis();
    System.out.println("bufferedWriteTest's time---------" + (start - end));

    //5.bufferedWrite And FileWriterTest's time
    start = System.currentTimeMillis();
    t.bufferedWriteAndFileWriterTest(count, str);
    end = System.currentTimeMillis();
    System.out.println("bufferedWrite And FileWriterTest's time---------" + (start - end));

    //6.bufferedWrite And BufferedOutputStreamTest's time
    start = System.currentTimeMillis();
    t.bufferedWriteAndBufferedOutputStreamTest(count, str);
    end = System.currentTimeMillis();
    System.out.println("bufferedWrite And BufferedOutputStreamTest's time---------" + (start - end));
}

测试结果：

　　

/**
 * 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
  */

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。实际上用的6.