java 线程安全 锁

package test;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import net.sf.json.JSONObject;

import com.hlzt.wx.util.http.WxHttpClientUtils;
import com.hlzt.wx.util.msg_handler.MsgDispatcher;

public class ss {

public static void main(String[] args) throws UnsupportedEncodingException {
ddd d=new ddd("aaaaaaaaaaaaaa");
d.start();
ddd d2=new ddd("bbbbbbbbbbbbbb");
d2.start();

}

public synchronized static void aa(String str)
{
System.out.println("1#########"+str);
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

System.out.println("2#########"+str);

}

}

class ddd  extends Thread{
private String aaa;

public ddd(String aaa) {
this.aaa = aaa;
}

@Override
public void run() {
ss.aa(aaa);
}

}