由兩個線程併發修改HashMap

如果兩個線程嘗試將（鍵，值）放入同一個映射中傳遞給線程的構造函數。我可能遇到什麼樣的線程問題？由兩個線程併發修改HashMap

public class App { 
    public static void main(String[] args) throws JMSException { 
     Map<String, String> map = new HashMap<String, String>(); 
     map.put("5", "fnc"); 

     Thread t1 = new App().new T(map); 
     Thread t2 = new App().new T(map); 
     t1.start(); 
     t2.start(); 
    } 

    class T extends Thread { 

     private Map<String, String> map; 

     public T(Map<String, String> map) { 
      this.map = map; 
     } 

     public void run() { 
      // put 100s of keys in map here 
      map.put("1", "abc"); 
      // put other keys 
     } 
    } 
}

來源

2014-03-01 Tarun Kumar

對Oracle HashMap實現的併發讀取和寫入操作可能會導致掛起的線程（由於底層實現，很容易使其陷入無限循環）。請參閱http://stackoverflow.com/a/1068213/83695 – andersoj