Question

java中如何把一个文件转化为byte数组？

Answer 1

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

public class Test {

public static void main(String[] args) {

// TODO Auto-generated method stub

try{

getBytesFromFile(new File("C:\\aaa.txt"));

}catch(IOException e){

System.out.println("IOException");

}

}

// 返回一个byte数组

public static byte[] getBytesFromFile(File file) throws IOException {

InputStream is = new FileInputStream(file);

// 获取文件大小

long length = file.length();

if (length > Integer.MAX_VALUE) {

// 文件太大，无法读取

throw new IOException("File is to large "+file.getName());

}

// 创建一个数据来保存文件数据

byte[] bytes = new byte[(int)length];

// 读取数据到byte数组中

int offset = 0;

int numRead = 0;

while (offset < bytes.length

&& (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0) {

offset += numRead;

}

// 确保所有数据均被读取

if (offset < bytes.length) {

throw new IOException("Could not completely read file "+file.getName());

}

// Close the input stream and return bytes

is.close();

return bytes;

}

}

Answer 2

import java.io.*;

public class TestT {
public static void main(String[] args) throws IOException {
File doc = new File("目录/1.json");

FileInputStream fis = new FileInputStream(doc);
int fisByteNum = fis.available();
byte[] fisByte = new byte[fisByteNum];
fis.close();
}