将一个文件内的所有内容读取到byte数组，也可以把一个byte[]的内容写入到文件中。可以作为复制文件的方法

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class FileHelper {
//第一种获取文件内容方式
public byte[] getContent(String filePath) throws IOException {
File file = new File(filePath);

long fileSize = file.length();
if (fileSize > Integer.MAX_VALUE) {
System.out.println("file too big...");
return null;
}

FileInputStream fi = new FileInputStream(file);

byte[] buffer = new byte[(int) fileSize];

int offset = 0;

int numRead = 0;

while (offset < buffer.length

&& (numRead = fi.read(buffer, offset, buffer.length - offset)) >= 0) {

offset += numRead;

}

// 确保所有数据均被读取

if (offset != buffer.length) {

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

}

fi.close();

return buffer;
}

//第二种获取文件内容方式
public byte[] getContent2(String filePath) throws IOException
{
FileInputStream in=new FileInputStream(filePath);

ByteArrayOutputStream out=new ByteArrayOutputStream(1024);

System.out.println("bytes available:"+in.available());

byte[] temp=new byte[1024];

int size=0;

while((size=in.read(temp))!=-1)
{
out.write(temp,0,size);
}

in.close();

byte[] bytes=out.toByteArray();
System.out.println("bytes size got is:"+bytes.length);

return bytes;
}
        //将byte数组写入文件
public void createFile(String path, byte[] content) throws IOException {

FileOutputStream fos = new FileOutputStream(path);

fos.write(content);
fos.close();
}

}