java中读取文件的常用方法

通过流来测试File的用例，二进制可以传输文本，图像等文件。测试用例

```

package com.caoqiwen.io;

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.ByteArrayInputStream;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.util.Random;

import java.util.zip.DeflaterOutputStream;

/***

* 字节流的做法

* @author caoqiwen

*

*/

public class Demo5 {

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

byte[] arr = getBytesFromFile("F:/Android/Java/JavaDemo/JavaDemo2/2.txt");

int random = new Random().nextInt(100);

String name = String.valueOf(random);

String destPath = "F:/Android/Java/JavaDemo/JavaDemo2/" + name + ".txt";

toFileFromByteArray(arr, destPath);

}

//转换成byte数组

public static byte[] getBytesFromFile(String srcPath) throws IOException {

File file = new File(srcPath);

byte[] dest = null;

InputStream is = new BufferedInputStream(new FileInputStream(srcPath));

// 字节数组输出流

ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();

byte[] flush = new byte[1024];

int len = 0;

while (-1 != (len = is.read(flush))) {

byteArrayOutputStream.write(flush, 0, len);

}

byteArrayOutputStream.flush();

dest = byteArrayOutputStream.toByteArray(); // 转换成byte[]数组

byteArrayOutputStream.close();

is.close();

return dest;

}

public static void toFileFromByteArray(byte[] src, String destPath) throws IOException {

File dest = new File(destPath);

InputStream iStream = new BufferedInputStream(new ByteArrayInputStream(src));

OutputStream oStream = new BufferedOutputStream(new FileOutputStream(dest));

byte[] flush = new byte[1024];

int len = 0;

while (-1 != (len = iStream.read(flush))) {

oStream.write(flush, 0, len);

}

oStream.flush();

oStream.close();  //后面打开的先关闭

iStream.close();

}

}

```