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();
	}

	//写入
	public static void writeFile() throws IOException
	{
		FileOutputStream fos = new FileOutputStream("fos.txt");
		fos.write("abcd".getBytes());
		fos.close();
	}
	
	//读出
	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();
	}
}