測試 hashmap hashtable Collections.synchronizedMap 多線程併發安全

測試 hashmap  hashtable   Collections.synchronizedMap 多線程併發安全

//  private   static Hashtable<String,Integer > map = new Hashtable<String, Integer>();
  //  private   static Map<String,Integer > map = new HashMap<String, Integer>();
	     private   static Map<String,Integer > map = Collections.synchronizedMap(new HashMap());


	public static void main(String[] args) throws InterruptedException {
		map.put("key", 0);
 
			 ThreadA threadA=new ThreadA();
			 ThreadB threadB=new ThreadB();
			 threadA.start();
			 threadB.start();
			            
			 //這裏等待線程結束後,重置共享變量,以使驗證結果的工做變得簡單些.
			 threadA.join();
		 
			System.out.println(map.get("key"));
			for (int i = 0; i < 2000; i++) {
				 if(!String.valueOf(i).equals(String.valueOf(map.get(String.valueOf(i))))){
					  System.err.println(String.valueOf(i)+":"+map.get(String.valueOf(i)));
				 }
			}
	}

	static class ThreadA extends Thread {
		int kk = 0;

		public void run() {
			for (int i = 0; i < 1000; i++) {
				map.put(""+i,i);
			}

		}
	}

	static class ThreadB extends Thread {
		public void run() {
			for (int i = 1000; i < 2000; i++) {
				map.put(""+i,i);
			}

		}
	}