java生成时间戳

package cn.mldn.lxh.util;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;
public class IPTimeStamp {
	private SimpleDateFormat sdf = null;
	private String ip = null;
	public IPTimeStamp(){
					
	}
	public IPTimeStamp(String ip){
		this.ip = ip;		
	}
	public String getIPTimeRand(){
		StringBuffer buf = new StringBuffer();
		if(this.ip!=null){
			String s[] = this.ip.split("\\.");
			for(int i=0;i