1、字节流----对文件读取(速度慢)

/**

* 字节流---文件的读取，输出(缺点：速度慢)

*

* @throws Exception

*/

@Test

public void testIO1() throws Exception {

// 输入字节流对象

InputStream in = new FileInputStream("pkg/a.txt");

// 输出字节流对象

OutputStream out = new FileOutputStream("pkg/b.txt");

//这里定义个字节数组，用来指定每次读取的字节数

byte[] b = new byte[1024];

int len = -1;

while ((len = in.read(b, 0, b.length)) != -1) {

String str = new String(b, 0, len, "UTF-8");

System.out.println(str);

out.write(b, 0, len);

}

//关闭对象

out.close();

in.close();

}

2、带缓存的字节流---文件读取(速度快)

/**

* 缓存字节流---文件读取，输出(推荐：速度快)

*

* @throws Exception

*/

@Test

public void testIO2() throws Exception {

BufferedInputStream in = new BufferedInputStream(new FileInputStream("pkg/a.txt"));

BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream("pkg/b.txt"));

byte[] b = new byte[1024];

int len = -1;

while ((len = in.read(b, 0, b.length)) != -1) {

String str = new String(b, 0, len, "UTF-8");

System.out.println(str);

out.write(b, 0, len);

}

//刷新缓冲

out.flush();

//关闭流对象

in.close();

out.close();

}

3、字节流reader，这个方法不能指定读取的字节数(不推荐)

/*

* 字节流reader，不能指定字节长度读取，不建议使用

*/

@Test

public void testIO3() throws Exception {

InputStreamReader in = new InputStreamReader(new FileInputStream("pkg/a.txt"), "UTF-8");

OutputStreamWriter out = new OutputStreamWriter(new FileOutputStream("pkg/b.txt"));

int len = -1;

while ((len = in.read()) != -1) {

System.out.println(len);

// 写入文件

out.write(len);

}

out.flush();

in.close();

out.close();

}

4、带缓冲的字节流读取方式，readLine()

/**

* 另一种字节流读取方式----可以提供readLine()的方法，一次读取一行。

*

* @throws Exception

*/

@Test

public void testIO4() throws Exception {

BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream("pkg/a.txt"), "UTF-8"));

BufferedWriter out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("pkg/b.txt"), "UTF-8"));

String str;

while ((str = in.readLine()) != null) {

System.out.println(str);

out.write(str + "\n");

}

out.flush();

in.close();

out.close();

}

小结：实际在用的过程，肯定是选择带有缓冲区的字节流读取方式，另外能够指定每次读取的字节数最好不过了。因此，方式2 推荐使用。