在运行程序之前列出已修改的文件 [英] List out the files that has been modified before run the program

问题描述

您好。目前我有一个代码可以列出目录中最新修改的文​​件。下面是我的代码：

Hi. Currently I have a code that can list out the latest modified file in the directory. Below is my code:

		//store the file to the list
		List<File> list = new ArrayList<File>(Arrays.asList(store));
		//combine all the file at main folder and sub folder
		Object[] combine = list.toArray();
		//sort the file according to the date
		Arrays.sort(combine, new Comparator<Object>(){
			public int compare(Object o1, Object o2){
				return compare((File)o1, (File)o2);
			}
			public int compare( File f1, File f2){
				long StartTime = f2.lastModified() - f1.lastModified();
				if( StartTime > 0 ){
					return 1;
				}else if( StartTime < 0 ){
					return -1;
				}else {
					return 0;
				}
			}
		});
		//get the file name that has latest modified date
		files = ((File) combine[0]).getName();
		//get the file date that has latest modified date
		lastModifiedDate = new java.util.Date(((File)combine[0]).lastModified()).toString();
		System.out.println("The latest modified file is : "+files);
		System.out.println("The time for the latest modified's file is :");
		System.out.println(lastModifiedDate);
	}
}

当我修改目录中的文件并运行程序时，它可以列出我修改过的文件。但是当我在目录中修改了超过1个文件并运行程序时，它只能显示具有最新修改时间的文件。

我的问题是：如何列出所有文件在运行程序之前是否已被修改？

When i modified a file in the directory and run the program, it can list out the file that i has been modified. But when i modified more then 1 files in the directory and run the program, it can only show the file that has the latest modification time.
My question is: How can i list out all the files that has been modified before i run the program?

推荐答案

上次修改日期不准确，我可以将其设置为我喜欢的任何内容。对于实际使用，请使用SHA-2等加密函数。



MessageDigest，DigestInputStream等将为您提供帮助。

Last modified dates cannot be accurate, I can set it to anything I like. For real-world uses, use cryptographic functions like SHA-2.

MessageDigest, DigestInputStream etc. will help you.

Hashmap<string,string> map = new Hashmap<>();
//Populate the map with checksums while load or better while compile
//map.put("filea","checksum");

public boolean checkModified(String file) {
     File f = new File("some file");
     MessageDigest md = MessageDigest.getInstance("SHA-2");

     try(FileInputStream fin = new FileInputStream(file)) {
         byte[] buffer = new byte[1024]; //buffer
         int read = 0;
         while((read = fin.read(buffer,0,1024)) != -1)
         {
             md.update(buffer,0,read);
         }

         String digest = toHex(md.digest());
         //check against a prepopulated list of hashes
         return map.get(f.getName()).equals(digest); //some say that message digests should be compared bitwise not in string form?
         
     } catch (Exception e) {
        //return false;
     }
     return false;
}
private static String[] hexArray = {
"00","01","02","03","04","05","06","07","08","09","0A","0B","0C","0D","0E","0F",
"10","11","12","13","14","15","16","17","18","19","1A","1B","1C","1D","1E","1F",
"20","21","22","23","24","25","26","27","28","29","2A","2B","2C","2D","2E","2F",
"30","31","32","33","34","35","36","37","38","39","3A","3B","3C","3D","3E","3F",
"40","41","42","43","44","45","46","47","48","49","4A","4B","4C","4D","4E","4F",
"50","51","52","53","54","55","56","57","58","59","5A","5B","5C","5D","5E","5F",
"60","61","62","63","64","65","66","67","68","69","6A","6B","6C","6D","6E","6F",
"70","71","72","73","74","75","76","77","78","79","7A","7B","7C","7D","7E","7F",
"80","81","82","83","84","85","86","87","88","89","8A","8B","8C","8D","8E","8F",
"90","91","92","93","94","95","96","97","98","99","9A","9B","9C","9D","9E","9F",
"A0","A1","A2","A3","A4","A5","A6","A7","A8","A9","AA","AB","AC","AD","AE","AF",
"B0","B1","B2","B3","B4","B5","B6","B7","B8","B9","BA","BB","BC","BD","BE","BF",
"C0","C1","C2","C3","C4","C5","C6","C7","C8","C9","CA","CB","CC","CD","CE","CF",
"D0","D1","D2","D3","D4","D5","D6","D7","D8","D9","DA","DB","DC","DD","DE","DF",
"E0","E1","E2","E3","E4","E5","E6","E7","E8","E9","EA","EB","EC","ED","EE","EF",
"F0","F1","F2","F3","F4","F5","F6","F7","F8","F9","FA","FB","FC","FD","FE","FF"};

String toHex(byte[] array)
{
    StringBuffer sb = new StringBuffer();
    for(byte b : array)
    {
        hexString.append(hexArray[0xFF & b]);
    }
    return sb.toString();
}

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