直接插在文件上，读写文件数据
创建对象
new FileOutputStream(文件)
不管文件是否存在，都会信件一个空文件
new FileOutputStream(文件，true)
文件存在，追加数据
高级流、操作流
与其他流对接，提供特点的数据处理功能
对高级流的操作，会对详解的流执行相同操作

FileOutputStream

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

public class Test1OutputStream {
    public static void main(String[] args) throws IOException {
        FileOutputStream out = new FileOutputStream("f3");
        out.write(97);//00 00 00 61->61
        out.write(98);//00 00 00 62->62
        out.write(99);//00 00 00 63->63
        out.write(356);//00 00 01 64->64
        byte[] a={
                101,102,103,104,105,
                106,107,108,109,110
        };
        out.write(a);
        out.write(a, 2, 4);
        out.flush();
        out.close();
        System.out.println("写入完成");
    }
}

运行结果

写入完成

FileInputStream

import java.io.FileInputStream;
import java.io.IOException;
import java.util.Arrays;

public class Test2InputStream {
    public static void main(String[] args) throws IOException {
        FileInputStream in = new FileInputStream("f3");
        //单字节读取 5个一批
        readByte(in);
        in.close();
        //流只能顺序读取一次
        in = new FileInputStream("f3");
        //批量读取
        readMore(in);
        in.close();
    }

    private static void readMore(FileInputStream in) throws IOException {
        
        byte[] buff=new byte[5];
        int n;
        while((n=in.read(buff))!=-1)
        {
            System.out.println(n+" "+Arrays.toString(buff));
        }
        System.out.println();
        
    }

    private static void readByte(FileInputStream in) throws IOException {
        
        int b;
        while((b=in.read())!=-1)
        {
            System.out.print(b+" ");
        }
        System.out.println();
    }
}

运行结果

97 98 99 100 101 102 103 104 105 106 107 108 109 110 103 104 105 106 
5 [97, 98, 99, 100, 101]
5 [102, 103, 104, 105, 106]
5 [107, 108, 109, 110, 103]
3 [104, 105, 106, 110, 103]