java中log4j的问题，急，多谢

小弟除学java，想学习用log4j来写日志，用jbuilder写了个简单的只包含了个main函数的类，下载了log4j.jar，然后网上也找了好多文章，还是没有搞定log4j怎么用？

谁能说说到底怎么用啊？下面是我下载的源码：
package com.log；
import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;

public class Hello{
static Logger logger = Logger.getLogger(Hello.class);
public static void main(String[] args)
{
// BasicConfigurator.configure();
PropertyConfigurator.configure("log4j.inf");

logger.info("Entering application.");
}
}

log4j.inf 内容如下：
log4j.rootLogger=WARN,stdout,R

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

# Pattern to output the caller's file name and line number.
#log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n
# Print the date in ISO 8601 format
log4j.appender.stdout.layout.ConversionPattern=%d [%t] %-5p %c - %m%n

log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=example.log

log4j.appender.R.MaxFileSize=100KB
# Keep one backup file
log4j.appender.R.MaxBackupIndex=1

log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n

# Print only messages of level WARN or above in the package com.foo.
log4j.logger.com.foo=WARN


报错说log4j.inf找不到，不知道这个文件应该放到哪里？错误信息如下：
log4j:ERROR setFile(null,false) call failed.

java.io.FileNotFoundException: ..\log\server.log (The system cannot find the path specified)