Use CAS instead of synchronized

It needs to be often used in development synchronized Guarantee code Thread safety , Waiting resources will be blocked under competitive conditions , If you are allowed to compete for less than resources, return failure , You can use cas Reduce blocking time . Let's have a look at cas Single instance mode of .

public class NonBlock {
    
 
	private static volatile NonBlock nonBlock;
 
	private static AtomicBoolean atomicBoolean = new AtomicBoolean(false);
 
	public static NonBlock getInstance() {
    
		if (nonBlock == null) {
    
			if (atomicBoolean.compareAndSet(false, true)) {
    
				nonBlock = new NonBlock();
			}
		}
		return nonBlock;
	}
}

In this singleton mode , differ synchronized The block , Multi-threaded environment ,getInstance Ensure that only one object will be created , Possible return nonBlock Is an empty object . but , If it is allowed to return an empty object ,

	public class RedPacket {
    
 
		private long balance;
 
		private int num;
 
		public RedPacket(long balance, int num) {
    
			this.balance = balance;
			this.num = num;
		}
 
		public long get() {
    
			if (balance < 1 || num < 1) {
    
				return -1;
			}
			if (num == 1) {
    
				long result = balance;
				balance = 0;
				num--;
				return result;
			}
			long average = balance / num;
			long result = ThreadLocalRandom.current().nextLong(1, average * 2);
			balance -= result;
			num--;
			return result;
		}

We can also use cas Achieve the purpose of non blocking , This ensures thread safety , When there is competition, it indicates that the competition has failed , The exact point is to prompt that the balance may be greater than 0, Coming first may not be able to grab , Later, people can rob .

public class RedPacket {
    
 
		private long balance;
 
		private AtomicInteger num;
 
		public RedPacket(long balance, int num) {
    
			this.balance = balance;
			this.num = new AtomicInteger(num);
		}
 
		public long get() {
    
			int number = num.get();
			long balan = balance;
			if (balan < 1 || number < 1) {
    
				return -1;
			}
			if (num.compareAndSet(number, number - 1)) {
    
				if (number - 1 == 0) {
    
					balance = 0;
					return balan;
				}
				long average = balan / number;
				long result = ThreadLocalRandom.current().nextLong(1, average * 2);
				balance -= result;
			}
			return -1;
		}
	}