java多线程消费消息队列

package mutliThread;

import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

public class test {
 private static Queue<String> queue = new ConcurrentLinkedQueue<String>();
 private static final int threadNum = 3;

 public static void main(String[] args) throws Exception {
  insertThread it = new insertThread();
  it.start();
  ConcumerThread pt = new ConcumerThread();
  for (int i = 0; i < threadNum; i++) {
   pt = new ConcumerThread();
   pt.start();
  }
 }

 public static  boolean insert(String str) throws Exception {
  System.out.println("insert="+str+" , queue.size="+queue.size());
  queue.offer(str);
  
  if (queue.size() > 20000) {
   // do some thing
  }
  return true;
 }
  public synchronized static String get(){
   if(queue.isEmpty()){
    return null;
   }
  return queue.poll();
  }
}

class ConcumerThread extends Thread {
 public ConcumerThread() {

 }

 public void run() {
  String str = "";
  while (true) {
   str = test.get();
   if(str == null){
    System.out.println("任务池为空！");
    try {
     Thread.sleep(5*1000L);
    } catch (InterruptedException e) {
     e.printStackTrace();
    }
   }else{
    System.out.println(Thread.currentThread().getName()+"="+str);
   }
    
  }

 }
}
class insertThread extends Thread {
 public insertThread() {

 }

 public void run() {
  int i = 0;
  while (true) {
    try {
     test.insert("insert" + (i++));
    } catch (Exception e) {
     e.printStackTrace();
    }
  }

 }
}