package com.gota.demo.lj;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

public class FileChangedChecker {
	private String fileName;
	
	private MessageDigest md;
	
	private byte[] md5;
	private long lastModify;
	
	public FileChangedChecker(String fileName) {
		this.fileName = fileName;
		try {
			md = MessageDigest.getInstance("MD5");
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
	}
	
	public boolean checkByModifyTime() {
		File file = new File(fileName);
		long curModify = file.lastModified();
		boolean isChanged = curModify != lastModify; 
		if(isChanged)
			lastModify = curModify;
		return isChanged;
	}
	
	public boolean checkByMd5() {
		FileInputStream in = null;
		boolean isChanged = false;
		try {
			in = new FileInputStream(fileName);
			byte[] buf = new byte[in.available()];
			md.update(buf);
			byte[] curMd5 = md.digest();
			isChanged = !Arrays.equals(curMd5, md5);
			if(isChanged) md5 = curMd5;
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if(in != null) {
				try {
					in.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		return isChanged;
	}
	
}