before taday,I always read properties from file use by useing classes defined ,It is good luck for me to find the existent class to use when I read source of  log4j

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Properties;

public class test {

 //static Logger logger = Logger.getLogger(test.class);

 private static ClassLoader getTCL() throws IllegalAccessException,
   InvocationTargetException {

  // Are we running on a JDK 1.2 or later system?
  Method method = null;
  try {
   method = Thread.class.getMethod("getContextClassLoader", null);
  } catch (NoSuchMethodException e) {
   // We are running on JDK 1.1
   return null;
  }

  return (ClassLoader) method.invoke(Thread.currentThread(), null);
 }

 static public URL getResource(String resource) {
  ClassLoader classLoader = null;
  URL url = null;

  try {
   classLoader = getTCL();
  } catch (IllegalAccessException e) {
   // TODO 自动生成 catch 块
   e.printStackTrace();
  } catch (InvocationTargetException e) {
   // TODO 自动生成 catch 块
   e.printStackTrace();
  }

  url = classLoader.getResource(resource);

  return url;

 }

 public static void main(String argv[]) {
  //  BasicConfigurator.configure();
  //  logger.debug("Hello world.");
  //  logger.info("What a beatiful day.");
  
  Properties props = new Properties();
  java.net.URL configURL;
  try {
   configURL = getResource("b.txt");
   props.load(configURL.openStream());
   String value = props.getProperty("a");
   System.out.print(value);
  } catch (MalformedURLException e) {
   // TODO 自动生成 catch 块
   e.printStackTrace();
  } catch (IOException e1) {
   // TODO 自动生成 catch 块
   e1.printStackTrace();
  }
 }
}

in properties file,# is remark