1.使用FileInputStream读取文件

package peixun;

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

public class ReadByteStream {

    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("text.txt");
            
            byte input[] = new byte[21];
            
            fis.read(input);//读取字节流文件
            
            String inputString = new String(input);//将字节流文件转换成字符串
            
            System.out.println(inputString);
            
            
        }   
            
        catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
        
    }

}

2.使用FileOutputStream写入文件

package peixun;

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

public class WriteByteStrean {

    public static void main(String[] args) throws FileNotFoundException {
        try {
            FileOutputStream fos  = new FileOutputStream("textw.txt");//流的打开
            
            String outString = "write 123456写出数据";
            
            byte[] output = outString.getBytes();//流的写入，将文本文件获取为字节数组
            
            fos.write(output);//流的读取
            
            fos.close();//关闭流操作
            
        }
            
            catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        
    }

}

3.使用输入、输出流实现文件的拷贝

package peixun;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;

public class CopyByByteStream {

    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("123.png");//读取文件数据
            FileOutputStream fos = new FileOutputStream("123_new.png");
            
            byte [] input = new byte[50];
            
            while (fis.read(input) != -1) {
                fos.write(input);//将数组写出到新的文件
                
            }
            
            fis.close();
            fos.close();
            System.out.println("done");
            
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

4.使用缓冲的字节流读写数据：

package peixun;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class ReadByBufferedByteStream {

    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("1.mp4");
            BufferedInputStream bis = new BufferedInputStream(fis,100000);//设置缓冲区大小，一般大于数组的大小。
            FileOutputStream fos = new FileOutputStream("2.mp4");
            BufferedOutputStream bos = new BufferedOutputStream(fos,100000);
            
            byte [] input = new byte[100];//大型的文件对应的数组大一点，比较小的文件数组小一点。
            int count = 0;
            long before = System.currentTimeMillis();
            while (bis.read(input) != -1) {
                bos.write(input);
                count++;
            }
            bis.close();
            fis.close();
            fos.close();
            bos.close();
            System.out.println("count:"+count);
            System.out.println(System.currentTimeMillis()-before);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        
    }

}