输出流:OutputStream,常用子类:FileOutputStream
输入流:InputStream,常用子类:FileInputStream

• 输出流常用的案例用法:

package demoByteOut;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class OutputStream1 {
    public static void main(String[] args) {
        Out();
    }
    public static void Out() {
        OutputStream os = null;
        //创建输出文件
        try {
            os = new FileOutputStream("a.txt");
//          os = new FileOutputStream(new File("a.txt"));
//          os = new FileOutputStream("a.txt", true);
//          os = new FileOutputStream(new File("a.txt")，true);
            String str = "helloworld";
            byte[] bs = str.getBytes();
            //将指定字节写入此文件输出流。
            for(byte b : bs) {
                os.write(b);
            }
            //将 b.length 个字节从指定 byte 数组写入此文件输出流中。
            os.write(bs);
            //将指定 byte 数组中从偏移量 off 开始的 len 个字节写入此文件输出流。
            os.write(bs, 0, 5);
            os.flush();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }catch(IOException e) {
            e.printStackTrace();
        }finally {
            try {
                os.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

• 输入常用的案例方法:

package demoByte;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

public class InputSteam1 {

    public static void main(String[] args) {
        input3();
    }
    /**
     * 1.方法为单个字节读取
     * 2.效率太低
     */
    public static void input() {
        InputStream is = null;
        try {
            //创建字节输入流对象
            is = new FileInputStream("a.txt");
            //单个字节读取
            int num = is.read();
            System.out.println(num);
            System.out.println((char) num );
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }catch(IOException e) {
            e.printStackTrace();
        }
    }
    /**
     * 向整个文件读取数据
     */
    public static void input2() {
        InputStream is = null;
        try {
            //创建字节输入对象
            is = new FileInputStream("a.txt");
            //定义一个字节数组
            byte[] by = new byte[1024];
            //向字节数组中存储数据,返回读取长度
            int number= is.read(by);
            System.out.println(number);
            System.out.println(new String(by,0,number));
            } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }catch(IOException e) {
            e.printStackTrace();
        }
    }
    /**
     * 向整个文件读取一定的字节 
     */
    public static void input3() {
        InputStream is = null;
        try {
            //创建字节输入对象
            is = new FileInputStream("a.txt");
            //定义一个字节数组
            byte[] by = new byte[1024];
            int len = is.read(by,1,8);
            System.out.println(len);
            System.out.println(new String(by,1,len));
            } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }catch(IOException e) {
            e.printStackTrace();
        }
    }
}