IO-内存操作流、管道流、打印流

内存操作流

ByteArrayInputStream：主要将内容写入内存

ByteArrayOutputStream：主要将内容从内存输出

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class IOOperation {
	public static void main(String[] args) throws IOException {
		String str = "ROLLENHOLT";
		byte[] byteArr = str.getBytes();
		ByteArrayInputStream in = new ByteArrayInputStream(byteArr);
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		int temp = 0;
		while ((temp = in.read()) != -1) {
			char ch = (char) temp;
			out.write(Character.toLowerCase(ch));
		}
		String outStr = out.toString();
		in.close();
		out.close();
		System.out.println(outStr);
	}
}

运行结果：rollenholt

 

管道流

管道流主要可以进行两个线程之间的通信。

PipedOutputStream：管道输出流

PipedInputStream：管道输入流

import java.io.IOException;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;

/**
 * 消息发送类
 */
class Send implements Runnable {

	private PipedOutputStream out = null;

	public Send() {
		this.out = new PipedOutputStream();
	}

	public PipedOutputStream getOut() {
		return this.out;
	}

	@Override
	public void run() {
		String message = "hello , Rollen";
		try {
			out.write(message.getBytes());
		} catch (IOException e) {
			e.printStackTrace();
		}
		try {
			out.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

/**
 * 接受消息类
 */
class Recive implements Runnable {

	private PipedInputStream input = null;

	public Recive() {
		input = new PipedInputStream();
	}

	public PipedInputStream getInput() {
		return this.input;
	}

	@Override
	public void run() {
		byte[] b = new byte[1024];
		int len = 0;
		try {
			len = input.read(b);
		} catch (IOException e) {
			e.printStackTrace();
		}
		try {
			input.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		System.out.println("接受的内容为：" + new String(b, 0, len));
	}
}

public class IOOperation {
	public static void main(String[] args) throws IOException {
		Send send = new Send();
		Recive recive = new Recive();
		// 管道连接
		send.getOut().connect(recive.getInput());
		new Thread(send).start();
		new Thread(recive).start();
	}
}

运行结果：接受的内容为：hello , Rollen

 

打印流

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;

public class IOOperation {
	public static void main(String[] args) throws IOException {
		String fileName = "D:" + File.separator + "hello.txt";
		File f = new File(fileName);
		PrintStream print = new PrintStream(new FileOutputStream(f));
        print.println("Rollen");
        print.close();
	}
}

运行结果：文件中写入Rollen

 

打印流格式化输出

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;

public class IOOperation {
	public static void main(String[] args) throws IOException {
		String fileName = "D:" + File.separator + "hello.txt";
		File f = new File(fileName);
		PrintStream print = new PrintStream(new FileOutputStream(f));
		String name = "Rollen";
		int age = 20;
		print.printf("姓名：%s. 年龄：%d.", name, age);
		print.close();
	}
}

运行结果：文件中写入 姓名：Rollen. 年龄：20.

 

使用OutputStream向屏幕上输出内容

import java.io.IOException;
import java.io.OutputStream;

public class IOOperation {
	public static void main(String[] args) throws IOException {
		OutputStream out = System.out;
		out.write("Hello".getBytes());
		out.close();
	}
}

运行结果：输出Hello

 

输入输出重定向

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;

public class IOOperation {
	public static void main(String[] args) throws IOException {
		// 此刻直接输出到屏幕
		System.out.println("hello");
		String fileName = "D:" + File.separator + "hello.txt";
		File f = new File(fileName);
		System.setOut(new PrintStream(new FileOutputStream(f)));
		System.out.println("这些内容在文件中才能看到哦！");
	}
}

运行结果：第一个打印语句输出到屏幕，第二个打印语句输出到hello.txt文件

 

System.in重定向

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class IOOperation {
	public static void main(String[] args) throws IOException {
		String fileName = "D:" + File.separator + "hello.txt";
		File f = new File(fileName);
		if (!f.exists()) {
			return;
		} else {
			System.setIn(new FileInputStream(f));
			byte[] b = new byte[1024];
			int len = System.in.read(b);
			System.out.println(new String("读入的内容：" + new String(b, 0, len)));
		}
	}
}