Java简单U盘检测程序，思想是用File类比较操作系统中的盘符变化，并在新增盘符中搜索文件：

testU.java文件内容：

package testu;

import java.io.File;

import java.util.Vector;

import java.util.logging.Level;

import java.util.logging.Logger;

/**

*

* @author jys1109

*/

public class testU implements Runnable {

private File[] roots = File.listRoots();

private Vector fileVector = new Vector();

public testU() {

}

public void run() {

System.out.println("check system start...");

while (true) {

File[] tempFile = File.listRoots();

boolean sign = false;

fileVector.removeAllElements();

if (tempFile.length > roots.length) {

for (int i = tempFile.length - 1; i >= 0; i--) {

sign = false;

for (int j = roots.length - 1; j >= 0; j--) {

if (tempFile[i].equals(roots[j])) {

sign = true;

}

}

if (sign == false) {

fileVector.add(tempFile[i]);

System.out.println("Enter:" + tempFile[i].toString());

}

}

roots = File.listRoots();//update roots

new FindFileThread(fileVector).start();//find files thread

} else {

for (int i = roots.length - 1; i >= 0; i--) {

sign = false;

for (int j = tempFile.length - 1; j >= 0; j--) {

if (tempFile[j].equals(roots[i])) {

sign = true;

}

}

if (sign == false) {

System.out.println("Quit:" + roots[i].toString());

}

}

roots = File.listRoots();//update roots

}

try {

Thread.sleep(1000);

} catch (InterruptedException ex) {

Logger.getLogger(testU.class.getName()).log(Level.SEVERE, null, ex);

}

}

}

public static void main(String args[]) {

new Thread(new testU()).start();

}

}

其中FindFileThread类为搜索文件的守护线程代码如下：

package testu;

import java.io.File;

import java.util.Vector;

/**

*

* @author jys1109

*/

public class FindFileThread extends Thread {

private Vector fileVector = null;

private int scanNum = 1;

public FindFileThread(Vector fileVector) {

this.fileVector = fileVector;

}

@Override

public void run() {

while (scanNum <= fileVector.size()) {

try {

System.out.println("search:"+ fileVector.elementAt(scanNum - 1).toString());

getFiles(fileVector.elementAt(scanNum - 1).toString());

scanNum++;

} catch (Exception e) {

System.out.println("error");

scanNum++;

}

}

}

public void getFiles(String path) throws Exception {

try {

File file = new File(path);

if (file.isDirectory()) {

File[] fList = file.listFiles();

for (int j = 0; j < fList.length; j++) {

if (fList[j].isDirectory()) {

getFiles(fList[j].getPath()); //recursion

}

if (fList[j].getName().endsWith(".java")) {

System.out.println(fList[j]);

}

}

}

} catch (Exception e) {

System.out.println("Error:" + e);

}

}

}

编译运行结果：

插入U盘测试：搜索后缀名为.java的文件

拔出U盘时：