nio.2 nio 和传统io

java nio.2  主要提供了Paths和Files这两个队文件的访问类。

Files提供了操作文件的便捷方式：

1.  
复制文件 copy

 

//传统io
try
(
FileInputStream fis = new FileInputStream(new File("d:/1.jpg"));
FileOutputStream fos = new FileOutputStream(new File("d:/2.jpg"));)
{
int length = 0;
byte[] buffer = new byte[1024];
while(-1 != (length = fis.read(buffer, 0, buffer.length)))
{
fos.write(buffer, 0, length);
}
}
catch (Exception e)
{
e.printStackTrace();
}
//nio
try
(
FileChannel in = new FileInputStream(new File("d:/1.jpg")).getChannel();
FileChannel out = new FileOutputStream(new File("d:/2.jpg")).getChannel();)
{
ByteBuffer buffer = ByteBuffer.allocate(32);
while(-1 != (in.read(buffer)))
{
buffer.flip();
out.write(buffer);
buffer.clear();
}
}
catch (Exception e) {
e.printStackTrace();
}
//java7 中的Files操作
Files.copy(Paths.get("d:/1.jpg"), new FileOutputStream(new File("d:/2.jpg")));

 

总结：

传统io和nio最大的不同就是是按“水滴”取水，还是按“竹筒”取水，一个按字节，一个按块（buffer），而Files类提供的静态方法就是进行了一次封装而已。

 

2.   从文件中读：

文本文件获得List<String>readAllLine

二进制文件获得字节数组（注意不适合大文件） readAllByte

//传统io
try
(
BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream("d:/poem.txt")));)
{
String temp = null;
while(null != (temp = reader.readLine()))
{
System.out.println(temp);
}
}
//nio
try
(
FileChannel in = new FileInputStream(new File("d:/poem.txt")).getChannel();)
{
MappedByteBuffer buffer = in.map(FileChannel.MapMode.READ_ONLY, 0, new File("d:/poem.txt").length());
Charset charset = Charset.forName("GBK");
CharBuffer cb = charset.decode(buffer);
System.out.println(cb);
}
//java7 nio.2
List<String> list = Files.readAllLines(Paths.get("d:/poem.txt"), Charset.forName("GBK"));
for(String s: list)
{
System.out.println(s);
}

 

3.   写入文件

//传统io
try
(
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("d:/poem_bak.txt")));)
{
writer.write("闲居少邻并， 草径入荒园。\r\n");
writer.write("鸟宿池边树， 僧敲月下门。");
}

//nio
try
(
FileChannel out = new FileOutputStream("d:/poem_bak2.txt").getChannel();)
{
//发现channel读写只能针对bytebuffer，不知是不是？？？
CharBuffer cb = CharBuffer.wrap("闲居少邻并， 草径入荒园。\r\n" + "鸟宿池边树， 僧敲月下门。");
ByteBuffer bb = Charset.forName("GBK").encode(cb);
out.write(bb);
}

//java7 nio.2
List<String> list = new ArrayList<>();
list.add("闲居少邻并， 草径入荒园。");
list.add("鸟宿池边树， 僧敲月下门。");
Path p = Paths.get("d:/poem_bak3.txt");
if(!Files.exists(p))
{
Files.createFile(p);
}
//最后一个参数是打开模式，append为追加
Files.write(p, list, Charset.forName("GBK"),StandardOpenOption.APPEND

4.   获得一些基本熟悉

Files.exists()

Files.isHidden()

Files.isWritable()

5.   遍历文件

Files.walkFileTree(Paths.get("d:/"), new SimpleFileVisitor<Path>()
{
@Override
public FileVisitResult visitFile(Path file,
BasicFileAttributes attrs) throws IOException
{
// TODO Auto-generated method stub
return super.visitFile(file, attrs);
}

//一共可以重写四个方法
});

 

6.   监听文件

7.   获得属性 attribute