java 把文件转化为字节数组

java 中如何把文件（file）转化字节数组呢？

方式一：

 /**
     * 文件转换为二进制数组
     *
     * @param file 文件对象
     * @return
     * @throws IOException
     */
    public static byte[] fileTobytes(final File file) throws IOException {
        byte[] data = null;
        if (file.exists()) {
            FileInputStream fileInputStream = new FileInputStream(file);
            int length = fileInputStream.available();
            data = new byte[length];
            fileInputStream.read(data);
            fileInputStream.close();
        }
        return data;
    }

 方式二：

/***
	 * read file ,convert file to byte array
	 * 
	 * @param file
	 * @return
	 * @throws IOException
	 */
	public static byte[] readBytes4file(File file) throws IOException{
		BufferedInputStream in = new BufferedInputStream(new FileInputStream(file));        
        ByteArrayOutputStream out = new ByteArrayOutputStream(1024);        
       
//        System.out.println("Available bytes:" + in.available());        
       
        byte[] temp = new byte[1024];        
        int size = 0;        
        while ((size = in.read(temp)) != -1) {        
            out.write(temp, 0, size);        
        }        
        in.close();        
       
        byte[] content = out.toByteArray();
        return content;
	}