NIO file 读取为字节数组

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
 
import org.apache.commons.codec.binary.Base64;
 
public class Test {
	
    public static void main(String[] args) throws IOException {
    	File f = new File("C:\\Users\\admin\\Desktop\\1\\2.png");
    	byte[] datas = readByNIO(f);
    	String encodeBase64String = Base64.encodeBase64String(datas);
    	System.out.println(encodeBase64String);
	}
    
    public static byte[] readByNIO(File file) throws IOException {
        checkFileExists(file);
        //1、定义一个File管道，打开文件输入流，并获取该输入流管道。
        //2、定义一个ByteBuffer，并分配指定大小的内存空间
        //3、while循环读取管道数据到byteBuffer，直到管道数据全部读取
        //4、将byteBuffer转换为字节数组返回
        FileChannel fileChannel = null;
        FileInputStream in = null;
        try {
            in = new FileInputStream(file);
            fileChannel = in.getChannel();
            ByteBuffer buffer = ByteBuffer.allocate((int) fileChannel.size());
 
            while (fileChannel.read(buffer) > 0) {
            }
            return buffer.array();
        } finally {
            closeChannel(fileChannel);
            closeInputStream(in);
        }
    }
    
    private static void checkFileExists(File file) throws FileNotFoundException {
        if (file == null || !file.exists()) {
            System.err.println("file is not null or exist !");
            throw new FileNotFoundException(file.getName());
        }
    }
 
    private static void closeChannel(FileChannel channel) {
        try {
            channel.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
 
    private static void closeOutputStream(OutputStream bos) {
        try {
            bos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
 
    private static void closeInputStream(InputStream in) {
        try {
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
 
}