IO流--字节流

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

import java.io.LineNumberReader;

import java.nio.Buffer;

public class io {

	public static void main(String[] args) throws IOException

	{

		writeFile();

		readFile1();

		readFile2();

	}

	//写出

	public static void writeFile() throws IOException

	{

		FileOutputStream fos = new FileOutputStream("fos.txt");

		fos.write("abcd".getBytes());

		fos.close();

	}

	//读入

	public static void readFile1() throws IOException

	{

		FileInputStream fis1 = new FileInputStream("fos.txt");

		int ch=0;

		while((ch=fis1.read())!=-1) //一个一个读

		{

			System.out.println((char)ch);

		}

		fis1.close();

	}

	public static void readFile2() throws IOException

	{

		FileInputStream fis2 = new FileInputStream("fos.txt");

		byte[] buf = new byte[1024]; //缓冲区

		int len = 0;

		while((len=fis2.read(buf))!=-1) //以数组大小读入  返回值是读入的个数

		{

			System.out.println(new String (buf,0,len));

		}

		fis2.close();

		FileInputStream fis3 = new FileInputStream("fos.txt");

		//fis2.available 文件中字节的个数

		int num = fis3.available();

		//定义一个刚刚好的缓冲区，不能用与文件很大的 和爆内存

		byte[] buf2 = new byte[fis3.available()];

		fis3.read(buf2);

		System.out.println(num+":"+new String(buf2));

		fis3.close();

	}

}