private Timer timer;    /** * 简易定时器 * @param delay  多久后开始执行。毫秒 * @param period 执行的间隔时间。毫秒 */  public void test(long delay, long period) {          timer = new Timer();          timer.schedule(new TimerTask() {              public void run() {                  //你 的 操作方法                  System.out.println(System.currentTimeMillis());              }          }, delay, period);  }

package classloader;  /**  * @author vma  */  // 自定义一个类加载器  public class DynamicClassLoader extends ClassLoader {      public Class<?> findClass(byte[] b) throws ClassNotFoundException {          return defineClass(null, b, 0, b.length);      }  package classloader;  import java.io.File;  import java.io.FileInputStream;  import java.io.IOException;  /**  * @author vma  */  public class ManageClassLoader {      DynamicClassLoader dc =null;      Long lastModified = 0l;      Class c = null;      //加载类， 如果类文件修改过加载，如果没有修改，返回当前的      public Class loadClass(String name) throws ClassNotFoundException, IOException{       if (isClassModified(name)){          dc =  new DynamicClassLoader();        return c = dc.findClass(getBytes(name));       }       return c;      }      //判断是否被修改过      private boolean isClassModified(String filename) {          boolean returnValue = false;          File file = new File(filename);          if (file.lastModified() > lastModified) {              returnValue = true;          }          return returnValue;      }         // 从本地读取文件         private byte[] getBytes(String filename) throws IOException {          File file = new File(filename);          long len = file.length();          lastModified = file.lastModified();          byte raw[] = new byte[(int) len];          FileInputStream fin = new FileInputStream(file);          int r = fin.read(raw);          if (r != len) {             throw new IOException("Can't read all, " + r + " != " + len);         }         fin.close();         return raw;     } }

class Thread1 extends Thread{   public void run(){ //调用业务方法（查看文件是否改变） Thread.currentThread().sleep("100000"); }