java中的IO:节点流的使用

目录

1.文件字节流
2.文件字符流
3.字节数组流
4.管道流

 

1.文件字节流

1.1FileIputStream输入流

read()	从此输入流读取一个字节,返回读取的数据字节,达到文件末尾则返回-1.
read(Byte[] b)	从此输入流读取b.length个字节存入b中,返回读取到的有效字节个数,达到文件末尾则返回-1.
close()	关闭此输入流并释放资源

1.2FileOutputSteam输出流

write(int b)	将指定字节写入到此输出流
write(byte[] b, int off, int len)	将指定byte数组中从off开始的len个字节写入到此输出流
flush()	刷新此输出流并强制写出所有缓冲的输出字节
close()	关闭此输出流并释放资源

1.3实现文件复制

public class FileStreamDemo {

	// 每次读写一个字节
	public static void copy1(File src, File dest) throws IOException {
		FileInputStream fis = new FileInputStream(src);
		FileOutputStream fos = new FileOutputStream(dest);
		int value = fis.read();
		while (value != -1) {
			fos.write(value);
			value = fis.read();
		}
		fos.close();
		fis.close();
	}

	// 每次读写字节数组
	public static void copy2(File src, File dest) throws IOException {
		FileInputStream fis = new FileInputStream(src);
		FileOutputStream fos = new FileOutputStream(dest);
		byte[] temp = new byte[1 << 15];
		int value = fis.read(temp);
		while (value != -1) {
			fos.write(temp, 0, value);
			value = fis.read(temp);
		}
		fos.close();
		fis.close();
	}

	public static void main(String[] args) throws IOException {
		copy1(new File("c:\\a1.txt"), new File("d:\\b1.txt"));
		copy2(new File("c:\\a2.jpg"), new File("d:\\b2.jpg"));
	}
}

 

2.文件字符流

字符流与字节流的用法基本相同,是为了更便捷的读写文字,但是对于其他资源或文件读写会发生错误.利用字符流实现文件复制:

public class File_Reader_Writer {

	// 通过字符流复制文本文件
	public static void copy3(File src, File dest) throws IOException {
		FileReader fr = new FileReader(src);
		FileWriter fw = new FileWriter(dest);
		// 通过char类型数组读写
		char[] temp = new char[1 << 15];
		int value = fr.read(temp);
		while (value != -1) {
			fw.write(temp, 0, value);
			value = fr.read(temp);
		}
		fw.close();
		fr.close();
	}

	public static void main(String[] args) throws IOException {
		copy3(new File("c:\\a3.txt"), new File("d:\\b3.txt"));
	}
}

 

3.字节数组流

3.1字节数组输入流ByteArrayInputStream

面向数组,读方法与文件流相似.例:

public class ByteArrayInputStreamDemo {

	public static void main(String[] args) throws IOException {
		byte[] b = new byte[] { 23, 4, 54, 46, 78, 46, 78, 34, 84, 4 };
		ByteArrayInputStream bis = new ByteArrayInputStream(b);
		int temp = 0;
		while ((temp = bis.read()) != -1) {
			System.out.println(temp);
		}
	}
}

3.2字节数组输入流ByteArrayOutputStream

写方法除了write()以外,还提供了toByteArray()的方法,将输出流中的有效内容复制到该数组中.例:

public class ByteArrayOutputStreamDemo {

	public static void main(String[] args) throws IOException {
		final Random r = new Random();
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		for (int i = 0; i < 10; i++) {
			bos.write(r.nextInt(100));
		}
		byte[] b = bos.toByteArray();
		System.out.println(Arrays.toString(b));
	}
}

 

4.管道流

管道流常用于线程,并且输入流和输出流需要建立联系.例:

public class PipedStreamDemo {

	public static void main(String[] args) throws Exception {
		// 创建线程任务
		Send s = new Send();
		Receive r = new Receive();
		// 连接两个管道流
		s.getOut().connect(r.getIn());
		// 启动线程
		new Thread(s).start();
		new Thread(r).start();
	}
}

class Send implements Runnable {
	private PipedOutputStream out = new PipedOutputStream();

	public PipedOutputStream getOut() {
		return out;
	}

	@Override
	public void run() {
		String message = "This is a PipedStream";
		try {
			out.write(message.getBytes());
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

class Receive implements Runnable {
	private PipedInputStream in = new PipedInputStream();

	public PipedInputStream getIn() {
		return in;
	}

	@Override
	public void run() {
		byte[] b = new byte[1 << 10];
		int length = 0;
		try {
			length = in.read(b);
		} catch (IOException e) {
			e.printStackTrace();
		}
		System.out.println(new String(b, 0, length));
	}
}

 运行结果:This is a PipedStream