Java文件字节流

//输出和输入流

package com.kangkang.IO;

import com.sun.xml.internal.ws.util.xml.CDATA;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

public class demo01 {

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

//数据的写入

byte[] data = {15,5,63,46};

File file = new File("example.123");

FileOutputStream outputStream = new FileOutputStream(file);

    outputStream.write(data,0,4);
    outputStream.close();
    System.out.println("Exit..");
}

}

package com.kangkang.IO;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

public class demo02 {

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

//数据的读取

    //用于接收数据的缓冲区，需要足够大
    byte[] buffer = new byte[50];
    // 可以使用绝对路径，如c:/加文件的目录
    // 也可以使用相对路径，把文件放在项目目录下
    File file = new File("kangkang.txt");
    // 从文件读取数据，存放进缓存区
    FileInputStream inputStream = new FileInputStream(file);
    int n = inputStream.read(buffer,0,50);
    inputStream.close();
    System.out.println("获取了"+n+"字节");
    System.out.println("Exit");
    String str = new String(buffer,0,n,"UTF-8");
    System.out.println(str);
}

}

package com.kangkang.IO;

import java.io.File;

import java.io.FileOutputStream;

public class demo03 {

public static void main(String[] args) throws Exception{

//文件的写入

    //字符串
    String str = "康康你好帅";
    //因为文件里面全部都是字节形式，所以要把字符串转换为字节才能写入文件中
    byte[] data = str.getBytes("UTF-8");
    File file = new File("kang.999");
    FileOutputStream outputStream = new FileOutputStream(file);
    outputStream.write(data);

    outputStream.close();
    System.out.println("Exit");
}

}

package com.kangkang.IO;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

public class demo04 {

public static void main(String[] args) throws Exception {

// 读取文件的内容

    byte[] buffer = new byte[100];
    File file = new File("kangkang.txt");
    FileInputStream inputStream = new FileInputStream(file);
    int n =inputStream.read(buffer,0,100);
    System.out.println("读取了"+n+"字节");
    inputStream.close();
    // 写入用什么格式，解码的时候也要用什么格式
    String str = new String(buffer,0,n,"UTF-8");
    System.out.println(str);
    System.out.println("Exit");
}

}