JAVA比较文件是否相同

业务场景：
因需要对上传的图片与已上传的图片进行判重。

思路：
将文件转换为MD5值，比较值是否重复

业务方法：

/**
	 * 验证证还是重复
	 * @param photo 判重文件
	 * @param realPath	文件上传目录(需要与目录中进行比较)
	 * @return
	 * @throws Exception
	 */
	private String verification(String photo,String realPath, String extension)throws Exception {
		String message = "";
        String photoMd5 = ConvertMD5Tools.getMD5(photo);
        File file = new File(realPath);
        String[] filelist = file.list();
        for (int j = 0; j < filelist.length; j++) {
            File readfile = new File(realPath + "\\" + filelist[j]);
            if (!readfile.isDirectory()) {
                String absolutepath = readfile.getAbsolutePath();
                String photoFileMd5 = ConvertMD5Tools.getMD5(absolutepath);
                if (photoFileMd5.equals(photoMd5)) {
                    message = photo
                            + "与" + absolutepath.substring((absolutepath.lastIndexOf("\\") + 1), absolutepath.length())
                            + "文件内容一样！";
                    break;
                }
            }
        }
        if (!"".equals(message)) {
            return message;
        }
       
		return message;
	}

ConvertMD5Tools.java 转md5工具类:

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class ConvertMD5Tools {

	//通过图片本地路径拿到MD5
	public static String getMD5(String imagePath) throws NoSuchAlgorithmException, IOException {
	    InputStream in = new FileInputStream(new File(imagePath));
	    StringBuffer md5 = new StringBuffer();
	    MessageDigest md = MessageDigest.getInstance("MD5");
	    byte[] dataBytes = new byte[1024];
	    int nread = 0;
	    while ((nread = in.read(dataBytes)) != -1) {
	        md.update(dataBytes, 0, nread);
	    }
	    byte[] mdbytes = md.digest();
	    // convert the byte to hex format
	    for (int i = 0; i < mdbytes.length; i++) {
	        md5.append(Integer.toString((mdbytes[i] & 0xff) + 0x100, 16).substring(1));
	    }
		in.close();
	    return md5.toString().toLowerCase();
	}	
}