java 使用线程监控文件目录变化的实现方法

package com.file;import java.io.File;import java.util.ArrayList;import java.util.HashMap;import java.util.Iterator;import java.util.List;import java.util.Map;public class FilesMonitor implements Runnable {// 文件夹路径private String filePath = "D://t//user//local//test//";// 存放已读文件<即：缓存目录>private static Map<String, File> map = new HashMap<String, File>();@Overridepublic void run() {while (true) {try {// 设置每隔3秒检测一次Thread.sleep(3000);FileMonitor();} catch (InterruptedException e) {e.printStackTrace();}}}// 文件监听public void FileMonitor() {File[] files = getFiles(filePath, null);if (files != null && files.length > 0) {// 如果缓存中文件与读取的个数不一样的时候String fName = "";if (files.length != map.size()) {if (map.size() == 0) {for (File file : files) {fName = file.getName();map.put(fName, file);System.out.println("新增了文件：" + fName);}} else {// 如果减少了文件if (map.size() > files.length) {List<String> removeName = new ArrayList<String>();Iterator<String> iter = map.keySet().iterator();int j = 0;while (iter.hasNext()) {String key = iter.next();if (key != null && key.length() > 0) {for (File file : files) {fName = file.getName();if (fName.equals(key)) {j = 1;break;}}if (j != 1) {removeName.add(key);}j = 0;}}// 判断是否有删除的文件if (removeName.size() > 0) {for (String item : removeName) {map.remove(item);System.out.println("减少了文件：" + item);}}} else {for (File file : files) {fName = file.getName();if (!map.containsKey(fName.trim())) {map.put(fName, file);System.out.println("新增了文件：" + fName);}}}}} else {map.clear();for (File file : files) {fName = file.getName();map.put(fName, file);}}System.out.println("此时缓存中文件个数：" + map.size());}}/*** 文件读取* * @param filePath*      路径* @param fileName*      名称* @return 返回文件数组*/public File[] getFiles(String filePath, String fileName) {File[] files = null;if (fileName == null) {File doc = new File(filePath);if (doc.isDirectory()) {String[] fileNameArr = doc.list();if (fileNameArr.length > 0) {files = new File[fileNameArr.length];for (int i = 0; i < fileNameArr.length; i++) {fileName = fileNameArr[i];String fileAbsPath = filePath + fileName;File regInfoFile = new File(fileAbsPath);files[i] = regInfoFile;}}}} else {String path = filePath + fileName;File doc = new File(path);if (doc.isFile()) {files = new File[1];files[0] = doc;}}return files;}// 启动线程public void show() {FilesMonitor t = new FilesMonitor();Thread tread = new Thread(t);tread.setName("eshore");tread.start();}// Main测试public static void main(String[] args) {FilesMonitor t = new FilesMonitor();t.show();}}