InputStream与OutputStream以及其子类

Java类库中的I/O类分成输入和输出两个部分。通过继承，任何自InputStream或Reader派生而来的类都含有名为read()的基本方法，用于读取单个字节或者字节数组。同样，任何自OutputStream或Writer派生而来的类都含有名为write()的基本方法，用于写单个字节或字节数组。

下面介绍三种继承自InputStream的子类:

一、FileInputStream、FileOutputStream

FileInputStream，用于从文件中读取信息。FileOutputStream， 用于将信息写至文件。

具体代码实现如下:

public class InputStream1 {
	public static void main(String[] args) {
		String fileName = "D:"+File.separator+"file.txt";
		File file = new File(fileName);
		if(!file.exists()){
			try {
				file.createNewFile();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		//FileOutputStream、FileInputStream文件操作流
		try {
			OutputStream os = new FileOutputStream(file);
			String str = "大家好!";
			byte[] a = str.getBytes();
			os.write(a);
			os.close();
			InputStream in = new FileInputStream(file);
			byte[] b = new byte[(int) file.length()];
			in.read(b);
			in.close();
			System.out.println(new String(b));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}	

二、ByteArrayInputStream、ByteArrayOutputStream

ByteArrayInputStream允许将内存的缓存区当作InputStream使用。 ByteArrayInputStream在内存中创建缓冲区，所有送往"流"的数据都要放置在此缓冲区。

具体代码实现如下:

//ByteArrayInputStream、ByteArrayOutputStream
		try {
			ByteArrayOutputStream bos = new ByteArrayOutputStream();
			int a = 0;
			int b = 1;
			int c = 2;
			bos.write(a);
			bos.write(b);
			bos.write(c);
			//获取内存缓冲中的数据
			byte[] buf = bos.toByteArray();
			bos.close();
			ByteArrayInputStream bin = new ByteArrayInputStream(buf);
			int data = 0;
			while((data=bin.read())!=-1){
				System.out.println(data);
			}
			bin.close();
		} catch (IOException e) {
			e.printStackTrace();
		}

三、PipedInputStream、PipedOutputStream

PipedInputStream产生用于写入相关PipedOutputStream的数据,实现"管道化"概念。 PipedOutputStream任何写入其中的信息都会自动作为相关PipedInputStream的输出。实现"管道化"概念。

具体代码实现如下:

//PipedInputStream、PipedOutputStream
		Sender sender = new Sender();
		Receiver receiver = new Receiver();
		PipedOutputStream outStream = sender.getOutStream();
		PipedInputStream inStream = receiver.getInStream();
		try {
			//使用connection()方法将其相连。
			outStream.connect(inStream);
		} catch (Exception e1) {
			e1.printStackTrace();
		}
		sender.start();
		receiver.start();
	}
}
class Sender extends Thread{
	private PipedOutputStream outStream = new PipedOutputStream();
	public PipedOutputStream getOutStream() {
		return outStream;
	}
	public void run() {
		String info = "hello world!";
		try {
			outStream.write(info.getBytes());
			outStream.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

class Receiver extends Thread {
	private PipedInputStream inStream = new PipedInputStream();
	public PipedInputStream getInStream() {
		return inStream;
	}
	public void run() {
		byte[] buf = new byte[1024];
		try {
			inStream.read(buf);
			System.out.println("receive message from sender : "
					+ new String(buf));
			inStream.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}