Java control concurrency Atomicboolean Lock Volatile

One, as a switch

A. Atomicboolean

	Private Atomicboolean update = new Atomicboolean (false);
	public void init ()
	{
	   if (This.update.compareAndSet (False, True))
	   {
		   try{
			//Do some thing
		   }
		   finally{
			This.refresh.set (false);
		   }
	   }
	

B. Volatile

	Public volatile Boolean update = FALSE;
	public void init ()
	{
	    if (update = = False) {
	        update = true;
	        DP some thing
	    }
	}

Second, counter

A.atomicinteger

	private static  Atomicinteger a = new Atomicinteger (0);
	A.getandincrement ();

b.sychrognized + volatile

	private volatile int value;
	public int GetValue () {return value;}

    public synchronized int increment () {return
        value++;
    }

question: Here the volatile keyword to remove what will be different?

Answer: No, remove the time, multithreading, other threads will read the value cached in the Register

Third, with lock

	Private lock lock = new Reentrantlock ();
	public void M1 () {
		this.lock.lock (); 
		try{
			//do Some thing
		}finally{
			lock.unlock ();
		}